fix: align input and outputSchema for older MCP revisions

[lloydrichards]

Type

• Bug Fix

Description

There are some differences between how input and output schema's work between the 2025 and 2026 era (pre 2025, outputSchema was not supported). I had already implemented the fix for input, but missed it with the output.

const Result = Schema.Struct({
  value: Schema.String
}).annotate({ identifier: "IdentifiedResult" })

// Before
{
  "$ref": "#/$defs/IdentifiedResult",
  "$defs": {
    "IdentifiedResult": {
      "type": "object",
      "properties": { "value": { "type": "string" } },
      "required": ["value"]
    }
  }
}

// After
{
  "type": "object",
  "properties": { "value": { "type": "string" } },
  "required": ["value"],
  "$defs": {
    "IdentifiedResult": {
      "type": "object",
      "properties": { "value": { "type": "string" } },
      "required": ["value"]
    }
  }
}

Added a regression test just in case.

Related

• Closes DRAFT: McpServer.registerToolkit serves a non-object-rooted outputSchema in rc.116, which the MCP TypeScript SDK rejects #8315
• Closes EFF-1443

[changeset-bot]

🦋 Changeset detected

Latest commit: a9e0611

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 31 packages

Name	Type
effect	Patch
@effect/opentelemetry	Patch
@effect/vitest	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/ai-typesafe	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-deno	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-pglite	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/docgen	Patch
@effect/doctest	Patch
@effect/openapi-generator	Patch

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Bundle Size Analysis

Generated from PR build output; treat the content below as untrusted.

File Name	Current Size	Previous Size	Difference
arbitrary-combinators.ts	37.71 KB	37.71 KB	0.00 KB (0.00%)
basic.ts	6.87 KB	6.87 KB	0.00 KB (0.00%)
batching.ts	9.95 KB	9.95 KB	0.00 KB (0.00%)
brand.ts	6.45 KB	6.45 KB	0.00 KB (0.00%)
cache.ts	10.77 KB	10.77 KB	0.00 KB (0.00%)
config.ts	21.83 KB	21.83 KB	0.00 KB (0.00%)
differ.ts	20.67 KB	20.67 KB	0.00 KB (0.00%)
http-client.ts	21.94 KB	21.94 KB	0.00 KB (0.00%)
http-router.ts	36.96 KB	36.96 KB	0.00 KB (0.00%)
logger.ts	10.88 KB	10.88 KB	0.00 KB (0.00%)
metric.ts	9.02 KB	9.02 KB	0.00 KB (0.00%)
optic.ts	6.70 KB	6.70 KB	0.00 KB (0.00%)
pubsub.ts	15.10 KB	15.10 KB	0.00 KB (0.00%)
queue.ts	11.85 KB	11.85 KB	0.00 KB (0.00%)
schedule.ts	10.96 KB	10.96 KB	0.00 KB (0.00%)
schema-bigdecimal.ts	13.40 KB	13.40 KB	0.00 KB (0.00%)
schema-binary.ts	39.82 KB	39.82 KB	0.00 KB (0.00%)
schema-class.ts	20.38 KB	20.38 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	31.18 KB	31.18 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	26.60 KB	26.60 KB	0.00 KB (0.00%)
schema-string-transformation.ts	13.96 KB	13.96 KB	0.00 KB (0.00%)
schema-string.ts	11.55 KB	11.55 KB	0.00 KB (0.00%)
schema-template-literal.ts	15.70 KB	15.70 KB	0.00 KB (0.00%)
schema-toArbitrary.ts	37.24 KB	37.24 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	24.84 KB	24.84 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	19.61 KB	19.61 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	19.75 KB	19.75 KB	0.00 KB (0.00%)
schema-toFormatter.ts	19.85 KB	19.85 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	24.15 KB	24.15 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	19.89 KB	19.89 KB	0.00 KB (0.00%)
schema.ts	19.59 KB	19.59 KB	0.00 KB (0.00%)
stm.ts	12.80 KB	12.80 KB	0.00 KB (0.00%)
stream.ts	9.83 KB	9.83 KB	0.00 KB (0.00%)