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internal/mcp: tool section of design

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Describe our tool design. This is short because most of the interesting
part is in the JSON Schema section.

Change-Id: I017fca3055aef881285280a379e9f235bf95e75d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671355
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Bypass: Jonathan Amsterdam <jba@google.com>
This commit is contained in:
Jonathan Amsterdam 2025-05-08 17:25:21 -04:00
commit 908c91313e
1 changed files with 24 additions and 10 deletions
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34
design/design.md
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@ -366,15 +366,29 @@ Client.RemoveRoots
### Tools ### Tools
<!-- Add tools to a server with `AddTools`:
TODO(rfindley): ```
NewTool server.AddTools(
ToolOption mcp.NewTool("add", "add numbers", addHandler),
Server.AddTools mcp.NewTools("subtract, subtract numbers", subHandler))
Server.RemoveTools ```
--> Remove them with `RemoveTools`:
```
server.RemoveTools("add", "subtract")
```
#### JSON Schema We provide a convenient and type-safe way to construct a Tool:
```
// NewTool is a creates a Tool using reflection on the given handler.
func NewTool[TReq any](name, description string, handler func(context.Context, TReq) ([]Content, error), opts …ToolOption) *Tool
```
The `TReq` type is typically a struct, and we use reflection on the struct to
determine the names and types of the tool's input. `ToolOption`s allow further
customization of a Tool's input schema.
Since all the fields of the Tool struct are exported, a Tool can also be created
directly with assignment or a struct literal.
A tool's input schema, expressed as a [JSON Schema](https://json-schema.org), A tool's input schema, expressed as a [JSON Schema](https://json-schema.org),
provides a way to validate the tool's input. provides a way to validate the tool's input.
@ -406,13 +420,13 @@ The struct provides the names, types and required status of the properties.
Other JSON Schema keywords can be specified by passing options to `NewTool`: Other JSON Schema keywords can be specified by passing options to `NewTool`:
``` ```
NewTool(name, description, handler, NewTool(name, description, handler,
Property("count", Description("size of the inventory"))) Input(Property("count", Description("size of the inventory"))))
``` ```
For less common keywords, use the `Schema` option: For less common keywords, use the `Schema` option:
``` ```
NewTool(name, description, handler, NewTool(name, description, handler,
Property("Choices", Schema(&jsonschema.Schema{UniqueItems: true}))) Input(Property("Choices", Schema(&jsonschema.Schema{UniqueItems: true}))))
``` ```
Schemas are validated on the server before the tool handler is called. Schemas are validated on the server before the tool handler is called.