2b1d10093eInterceptor SEP has been moved from https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1763 to https://github.com/modelcontextprotocol/modelcontextprotocol/issues/2624 . This PR updates the SEP references over the codebase and import revised SEP Signed-off-by: Ukjae Jeong <jeongukjae@gmail.com>
3.6 KiB
3.6 KiB
SEP Conformance
Status of this Go SDK implementation against the SEP-2624 interceptor proposal.
Implemented
| Area | Notes |
|---|---|
| Validation interceptors | Parallel execution, severity-based blocking, fail-open support |
| Mutation interceptors | Sequential execution, priority ordering, payload threading via json.RawMessage |
| Interceptor metadata | Name, version, description, events, phase, priorityHint (polymorphic JSON), compat, configSchema, mode, failOpen |
| Event names | Constants for all standard server-side MCP methods; JSON-RPC method names used directly as event names |
| Protocol methods | interceptors/list for discovery, interceptor/invoke for invocation — both registered as custom JSON-RPC methods |
InterceptorChain (SEP) |
chain.Chain type with chain.ChainEntry objects pairing interceptor descriptors with MCP client sessions |
ChainEntry (SEP) |
chain.ChainEntry struct holds InterceptorInfo + *mcp.ClientSession |
| Chain discovery | chain.Chain.AddMCPServer() calls interceptors/list to discover interceptors from an MCP server |
| Chain execution | chain.Chain.Execute() invokes interceptors via interceptor/invoke on the appropriate server per entry |
InvokeResult envelope |
Per-interceptor result with interceptor name, type, phase, duration, validation/mutation result, mutated payload |
chain.ExecutionResult |
Aggregated chain result with status, results, finalPayload, validationSummary, abortedAt, totalDurationMs |
| JSON-RPC error mapping | Typed error data structs: -32602 for validation, -32603 for mutation, -32000 for timeout |
| Trust-boundary execution order | Request: validate (parallel) then mutate (sequential); Response: mutate (sequential) then validate (parallel) |
| Priority ordering | Mutators sorted by priorityHint.Resolve(phase) ascending, alphabetical tiebreak |
| Fail-open behavior | FailOpen: true interceptors log errors without aborting the chain |
| Audit mode | ModeAudit records results without blocking; mutated payloads not propagated |
| Timeout & context | Per-interceptor timeouts via InvokeParams.TimeoutMs, chain-level context cancellation, InvocationContext with principal/traceId |
| Receiving direction (client → server) | All server-side method calls intercepted via AddReceivingMiddleware |
| Capability declaration | Interceptor metadata injected into initialize response via Capabilities.Experimental |
| First-party (in-process) deployment | Server.LocalChain() creates an in-memory transport chain.Chain; interceptors invoked via JSON-RPC even in-process |
| Third-party and hybrid deployment | Chain entries can point to any *mcp.ClientSession — local (in-memory), stdio, or HTTP transport |
json.RawMessage payloads |
Interceptor handlers receive json.RawMessage via interceptor/invoke, matching the SEP's JSON-level payload model |
Not Implemented
| Area | SEP expects | Notes |
|---|---|---|
| Wildcard event matching | "*/request", "*/response", "*" |
matchesEvent does exact match only; wildcard patterns are planned |
| Server → client interception | Client features as interceptable events: "sampling/createMessage", "elicitation/create", "roots/list" |
Requires Server.AddSendingMiddleware support in the go-sdk |
| Per-interceptor config passthrough | ChainExecutionParams.Config map |
Wired through to InvokeParams.Config but not yet used by middleware |
| Remote interceptor servers | Connecting chain to external MCP servers over stdio/HTTP | Infrastructure is ready (chain.Chain.AddMCPServer accepts any *mcp.ClientSession); no convenience helpers yet |