Since cancellation is handled transparently, this type need not be
exported.
Change-Id: Id4e195b0c3bd49eca52587032a027ffa449eb9d1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672796
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Add a logical client session type back to the SDK, to bring it closer to
the design. Also, remove 'ConnectionOptions', which is better
implemented using middleware, and reimplement logging as a
LoggingTransport middleware, which is also added to the design.
Change-Id: I908b4f837d513ffc60ae5b6171a31519cffafebc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672795
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Update the design to mention our in-memory transport, since it is
generally useful, and update the implementation to use distinct types
for InMemoryTransport and StdIOTransport (the fact that they are both
implemented as an io.ReadWriteCloser is an implementation detail).
Change-Id: I8228ccf2092a56a730c113c4db105fb492cce112
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672715
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Commit-Queue: Robert Findley <rfindley@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Bypass: Robert Findley <rfindley@google.com>
Bring the Server implementation up to date with the spec by renaming
ServerConnection to ServerSession. Also update variable names, which
were in various states of disarray from the multiple renamings of this
type.
Change-Id: I4aec883db6d0500fb91e6daa51b702614877cf8a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672655
Auto-Submit: Robert Findley <rfindley@google.com>
TryBot-Bypass: Robert Findley <rfindley@google.com>
Commit-Queue: Robert Findley <rfindley@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Get the name and signature of the handler right.
Change-Id: I743aaaee45cc07a741ab8ad16e90e1b1d5519b64
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672336
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Change the type of CallToolParams.Arguments to json.RawMessage.
Change-Id: Ief16ef261b9f41566a1a16efc60a9382a8d414eb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672615
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
CallTool takes a tool name, arguments, and an options struct.
Also, pass the params to ToolHandler.
Update the design doc accordingly.
Change-Id: I21b7995b607bea976ad708ebb6ac0716018f39cb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672596
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
To ensure backward compatibility, every method in the spec now takes a
*Params struct and returns a *Result struct.
CallTools is an exception: we'll change that in the next CL.
Change-Id: I58835239c67582401b8c9c2d070702d270131c08
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672595
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Use pointers for the protocol's struct types, to future-proof against
them getting large.
Change-Id: I55b204080a41c8140539697ba264e502e912e613
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672575
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Also, make sure that NewBlobResourceContents creates a Blob.
Change-Id: I2f0fe2ac6410d6b155deb2c8643a40bc73e25cd4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672418
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
To be compatible with Go 1.23, we cannot use the
encoding/json "omitzero" option. Replace with a
custom MarshalJSON method.
Change-Id: Ied615ea04fb20e2459f9ed20ef03c81edbc74961
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672417
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Now that the protocol package is merged into the mcp package, clean up
the higher level 'Content' union types, in favor of types constructors.
Change-Id: I37bedb0ff0a296eef799ba65c37ca7f94ee1dbbe
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672415
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Bypass: Jonathan Amsterdam <jba@google.com>
In accordance with the updated design, merge the protocol package into
the mcp package. To do so, rename protocol.Content to WireContent and
protocol.ResourceContents to WireResource.
Also, remove some stray logging in readResource.
Change-Id: I76f61ce8d67dd3ac520ef2e1959ade0a0785a480
Reviewed-on: https://go-review.googlesource.com/c/tools/+/672375
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Implementation of resources.
This follows the design sketched in design/design.md, except for
Server.FileResourceHandler, which will be in a forthcoming CL.
As the spec recommends, the server verifies an incoming URI from the
client against its list of resources, to make sure the URI came from one
of them.
Some things that aren't in the design doc:
- I provide an exported function that creates a "resource not found"
jsonrpc2.WireEror error for server authors to return.
A wrinkle: the MCP spec defines the error code for
"resource not found" as -32002 [1]. That code is reserved for use
by implementations of JSON-RPC, not applications. That matters to us
because our JSON-RPC implementation already uses that code for the
"server closing" error. I filed a bug against MCP about it [2] and
chose a different code for the "resource not found" error.
- As a slight convenience, I fill in some fields in the
ReadResourceResult if the handler doesn't set them.
[1] https://modelcontextprotocol.io/specification/2025-03-26/server/resources#error-handling
[2] https://github.com/modelcontextprotocol/modelcontextprotocol/issues/509
Change-Id: I06153da982ea00748a3691ded923448a880cea2a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671363
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
- Change the names of some content-related types to better match
the spec. Most notably, rename Resource to EmbeddedResource,
because the former has a different meaning in the spec.
- Use []byte intead of string where the spec says "base64-encoded data."
- Unexport EmbeddedResource.ToWire.
Change-Id: I9f65efaadadda1b3abc0e58c64a743af1a72852c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671362
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Bypass: Jonathan Amsterdam <jba@google.com>
Commit-Queue: Jonathan Amsterdam <jba@google.com>
You can now write "*" for a name in a config to use the original
name.
Also, fix a bug in dealing with initialisms.
Change-Id: I4d5d0acb1200fff6500644457ec34c5026d63f9f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671361
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Add support for roots.
Change-Id: Ia50abc88f0047238272d698f30ce615b1a8fd486
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671360
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
What the spec calls "lists" of features (tools, prompts and so on)
are actually sets. Define a common data structure we can use to
implement all of them, and use it for server tools and prompts.
Change-Id: I257d0776b87a746ff23cd49ebcc7b317f4ea65e1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671359
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Discuss generated protocol types, and expand on the section on package
layout to make it clearer how they fit in to the SDK.
Change-Id: I3beaa86c2396e0cee41dcc8eac06d93c54cb96df
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671016
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Expose the SSEServerTransport type, so that clients can customize the
handling of sessions and endpoints by writing their own HTTP handler.
This is similar to the behavior of the typescript SDK.
Also, finish documenting transports in the design doc.
Change-Id: Ief5aa8424ba2946a9615e366969a4750f40224a8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671015
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Enhance the generator so that it recognizes initialisms like "Id" and
writes them in all caps, as is idiomatic for Go.
Also, fix the import path of jsonschema in the generated code.
Change-Id: Ib12e9fbd543d360035d5e324f0aefca584ac7c85
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670916
Auto-Submit: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Start writing up a formal design doc for an MCP SDK based on what we've
learned from the prototype. Include discussion of package layout,
jsonrpc2, and transport. Lay out the rest of the design sections,
leaving stub comments describing what they should cover.
Change-Id: Id0e5b408eac8c0acb5ef90a32d0d69473d8e83f0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670536
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
It's too confusing that you send server requests through the Client, and
send client requests through the ClientConnection. Rename
ClientConnection to ServerConnection, so that the types on the
server side of the control diagram start with 'Server'.
Change-Id: Idfd27af464a9296a2341cd23b2075cd9d0eb6b45
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670538
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Pass the client Transport to NewClient instead of Connect.
Combine the ConnectionOptions with the ClientOptions.
Change-Id: I3acd6cf6d5bf46666742f2a73e2acaef2057ea77
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670215
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Move examples from package doc to README.md with package decl and
imports to ensure it's compilable.
Move status of the package from package doc to README.md.
Add core concepts of MCP with example code snippets and testing
recommendations.
Change-Id: I5bf5000b922fa3942aba922713b12d0347295811
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670316
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
The generated protocol package is part of the SDK API, so it shouldn't
be internal.
Change-Id: I5306af48019b1599707b939b348eb6ae4f766ca9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/670356
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
The jsonschema package is part of of the API of the mcp package,
so it should not be internal.
Change-Id: I9520797837329fc2cda09c2f46ec4d48d031b9d3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669996
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
This is the first CL that deals with the process of preparing a schema for validation.
Perform some basic checks on the scheme. Along the way, compile regexps and store
them in the schema for use during validation.
Change-Id: I0e5e6ce28656dcecb6d2d4b2fdc98998fa05b6f1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669696
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Remove ServerConnection.
- It's not in typescript or mcpgo APIs.
- Amortizing a client over multiple servers doesn't have any value.
Change-Id: I725b42569733d6836864d96b16898a10ae91e570
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669575
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Add support for all content types, and formalize the conversion of
content to and from the wire format (as a discriminated union).
Change-Id: I93678ce98c02176a524d2c82425fb1267ad68bf0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669135
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Reviewed-by: Jonathan Amsterdam <jba@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Add support for 'prompts/list' and 'prompts/get', and registering
prompts on the server using AddPrompts. Add a 'MakePrompt' helper to
construct prompts from a prompt handler using reflection.
Change-Id: I479cb9c9b99313cca99640c1f5ea1939363759e6
Reviewed-on: https://go-review.googlesource.com/c/tools/+/669015
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Implement variadic options for building tools and schemas, to allow
easier customization of tool input schemas.
Also, make fields required, unless they are marked as "omitempty".
Change-Id: I7a29258fae3ec5e7ea4906ed30ed6750979de962
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668955
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Add more documentation for the mcp package, explaining how to create and
use Clients and Servers. Also add an example of using the SSEHandler to
crete an MCP server.
Change-Id: Ib327826b2cdb1e3418482551c65569ec6f01af33
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668715
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Neal Patel <nealpatel@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Add a missing CommandTransport that communicates with a sidecar process
over newline-delimited stdin/stdout, the counterpart to the existing
StdIOTransport.
Add a test using the usual TestMain trick.
Change-Id: I170ba78faf6b6d7fca7da1af11bf92e919b11ed5
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668895
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Export the Transport interface, as there's no reason users shouldn't be
able to define their own transports: they are just bidirectional
streams.
Also, add a godoc example for basic Server usage.
Finally, remove some TODOs that existed due to a bad merge: they are
related to the (as yet unsubmitted) streamable HTTP transport.
Change-Id: Id669793fc80630e667d50611fe2876d09125a025
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668675
TryBot-Bypass: Robert Findley <rfindley@google.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
Based on my understanding, the getServer function is used to determine
which MCP server should be serving the session.
User might want to dynamically determine which MCP server to serve when
a new request comes in. In mcp/examples, two MCP servers are created
serving at the same port but under different URL "/greeter1",
"/greeter2". The MCP client will reach out to different URLs for
different MCP servers.
As a TODO, if the getServer() returns nil, the program will crash when
handing MCP request.
Change-Id: I4431266666e9ea28118e827a94eb1359b1fb3a81
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668535
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Hongxiang Jiang <hxjiang@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Add a bit more theory around SSE transport shutdown, and some
documentation of the SSE transport protocol itself. Additionally, remove
a TODO to avoid the use of channel buffering for message queues in http
transports; instead, always write to message buffers in a select
statement containing a read from the done channel. The bounded size of
message buffers then serves to create backpressure for an overloaded
server.
Change-Id: I5701c5b95a5ae73d796a634e434f41dfcdbddf51
Reviewed-on: https://go-review.googlesource.com/c/tools/+/668237
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Findley <rfindley@google.com>
The first of several CLs providing JSON Schema validation.
Replace the existing Schema type with one that has all the keywords
of the most current version of the JSON Schema spec, called 2020-12.
The 2020-12 spec can be represented type-safely in Go with one exception:
the "type" keyword can be either a string or a []string. To handle this
safely, both Type and Types fields are defined. Custom
JSONMarshal/Unmarshal methods handle the conversion. We need the
unmarshal anyway because "true" and "false" are valid schemas.
Unfortunately, the MCP spec uses the older "draft7" version of JSON
Schema, but the two are close enough for code generation to work.
I confirmed that the protocol generator produces the identical output.
Change-Id: I44f6ea2f3a3f8498979946f69dfb7f50afa1acad
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667855
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Use the existing jsonrpc2 preemption mechanism to implement MCP
cancellation.
This was mostly straightforward, except where I got confused about ID
unmarshaling. Leave a note about using omitempty when it is available.
Change-Id: I13e073f08c5d5c2cc78d882da4e6ff47f09fb340
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667578
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Also validate that requests observe the lifecycle rules defined in the
spec.
Change-Id: I302282f81e053e76926e0bb295f7dbf8d526f02d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667575
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Commit-Queue: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
TryBot-Bypass: Robert Findley <rfindley@google.com>
Add support for SSE transport, as defined by version 2024-11-05 and
2025-03-26 of the MCP spec.
In order to achieve this, the jsonrpc2 stream must be abstracted so that
we can implement it across multiple HTTP requests. This required some
refactoring of the jsonrpc2_v2 package, so that we can avoid the
Dialer/Binder interfaces and construct the Connection directly from its
constituent primitives.
Change-Id: Id627b5b5a474d92f2c613cfad904d14611e7c768
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667475
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Update the jsonrpc2 MCP framer to support both incoming and outgoing
batches. In order to achieve this, we must correlate the framed Reader
and Writer, which is not explicitly supported by the jsonrpc2 API, but
does work. A note is left to revisit the Framer interface.
Change-Id: If060cb5822da067833db20d58f5f112a0528da91
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667295
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This CL contains an minimal prototype of an MCP SDK, using the
"new" jsonrpc2_v2 package (similar to x/exp/jsonrpc2).
Much is still yet to do, but this initial version addressed the
following aspects:
- Support for newline delimited JSONRPC2 framing, and message logging.
- A generated protocol package, containing type definitions to be used
in transport.
- A minimal jsonschema package to be used for both reading the MCP spec,
and for serving Tool input schemas.
- A transport abstraction, and two transport implementations: stdio, and
local (for testing).
- Client and Server types, to be configured with features and then
connected using their Connect methods, which return (respectively) a
ServerConnection and ClientConnection object.
- A minimal binding API for tools.
A catalog of things not yet done is in doc.go, but we should review this
CL eagerly, as it contains the fundamental building blocks of an
eventual SDK.
It is the intention that this package is more-or-less standalone, as it
may eventually be carved out into a separate repository. As such, its
only dependency within x/tools is jsonrpc2_v2, and the only change
required to that package is to expose a callback when the connection is
closed.
Change-Id: Ib66018961014f85a8884d56ab721d5642c98443c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/667036
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
