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[2026-07-28] Schema modernization & error code standardization

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Quiet
Tech stack
php
Domain
api, backend

Research direction

Start with sub-issues #356–#359 and their SEP links. For the error-code work, inspect src/Schema/JsonRpc/Error.php and the protocol-version fallback described in the issue; for schema work, begin with the SchemaValidator and the listed JSON Schema vocabulary, outputSchema, structuredContent, SSRF, and DoS requirements. Done means all listed sub-issues are completed against the merged SEP requirements.

Written by the indexing model from the issue text.

Description

2026-07-28 enhancement improves spec compliance Schema

Tracking issue for the MCP Spec 2026-07-28 release — Schema & errors milestone.

SEPs covered

SEP Title Spec PR
SEP-2106 Tools inputSchema/outputSchema conform to JSON Schema 2020-12 #2106
SEP-2164 Standardize resource-not-found error code to -32602 #2164

Sub-issues

SEP-2106 (JSON Schema 2020-12):

  • #356 — Vocabulary support (oneOf/anyOf/allOf/if-then-else/$ref)
  • #357 — Allow non-object outputSchema and structuredContent
  • #358 — Harden SchemaValidator against external $ref SSRF and composition DoS

SEP-2164:

  • #359 — Switch resource-not-found error code to -32602 with protocol-version-aware fallback

Notes

  • Both SEPs are merged.
  • SEP-2106 is the largest code-level lift this cycle for the schema layer: full JSON Schema 2020-12 vocabulary (composition, conditionals, $ref), plus non-object outputSchema / structuredContent. Also requires hardening against external $ref SSRF and composition DoS.
  • SEP-2164 is mechanically a one-constant flip in src/Schema/JsonRpc/Error.php with a protocol-version-aware fallback.
Dominant language
PHP
Stars
1.6k
Forks
173
Avg merge
2d 49m
Merged PRs (30d)
23

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