mcpx: JSON Schema validation of tool inputs/outputs and elicitation schemas (7 conformance rows) #1951

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1. developing-today commented on Oct 28, 2026

   

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2. dezren39 commented on Oct 28, 2026

   

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   History carried over from dezren39/darwin-nix#254 (verbatim, oldest first):

   ---

   @dezren39 · 2026-10-02T08:56:04Z

   Reference implementation worth reading: https://github.com/wileai/codex-connectors-mcp validates tool arguments against each tool's original input schema -- draft-07, 2019-09 and 2020-12 -- without coercing or stripping, before dispatch. All three drafts are feasible: they differ mainly in definitions vs $defs, tuple items vs prefixItems, dependencies vs dependentRequired/dependentSchemas, and $recursiveRef vs $dynamicRef; the schema's $schema says which applies, 2020-12 when absent (the MCP default since 2025-11-25). Tracked under the codex-connectors adoption umbrella.

   ---

   @dezren39 · 2026-10-27T15:36:06Z

   Intake review

   Fleet monitor intake pass, 2026-10-27 (repo-fleet-monitor).

   Related: the 2026-09-30 mcpx conformance set — parent analysis #252, siblings #253, #254, #255, #256, #257, #258, #259 (filed together from docs/spec/conformance-matrix.md in dezren39/nix). Treat the set as one body of work; do not re-file per-gap issues.

   Notes: 7 conformance rows under the single gap key json-schema-validation. The body already names the key decision (validator choice) — that decision is the first deliverable, per the acceptance criteria.

   Risks: A hand-rolled validator that diverges from 2020-12 semantics on composition bounds; the matrix rows are the test oracle.

   Suggested approach: run the conformance rows against the existing internal/mcpspec subset validator first to size the gap before deciding on a dependency.

   ---

   @dezren39 · 2026-10-28T19:08:57Z

   Triage verdict (task 2306): LARGELY IMPLEMENTED since filing — remainder routed, issue stays open for it.

   Verified at developing-today/code main 35726e8e (mcpx source lives in pkgs/mcpx there):

   • Validator decision (acceptance 4): taken and recorded in pkgs/mcpx/docs/schema-validation.md and the internal/schemaval package doc — a dedicated runtime validator wrapping github.com/santhosh-tekuri/jsonschema/v6 (its only import site in the module); internal/mcpspec stays test-only for protocol frames. It was not recorded on this issue before implementation; this comment records it now.
   • Inputs (acceptance 1, first half): done. internal/mcpclient/schemacheck.go compiles schemas at list time (uncompilable tools excluded with a warning) and validateToolArgs rejects invalid arguments before transport with InvalidParamsError (mcpclient.TestCallToolRejectsInvalidArgumentsBeforeTheTransport).
   • Outputs (acceptance 1, second half): partial. checkToolOutput validates structuredContent against outputSchema but is warn-only — violations are delivered unchanged, not spec-correct errors. Whether that is the intended policy was never recorded.
   • Elicitation (acceptance 2): schemas are compiled/validated with the same schemaval mechanism. (Validating elicitation answers is fix(id): coalesce LogSync ingest batches (#241) #255's gap, separate.)
   • Dialects (acceptance 3): done in code — absent $schema = 2020-12; declared dialects limited to 2020-12/2019-09/draft-07/draft-06/draft-04 with a typed UnsupportedDialectError; the compiler refuses all network $ref loading (UnresolvedRefError); schema size bounded at 1 MiB. Matrix rows for these are marked tested (schemaval.TestDeclaredDialectsCompile, schemaval.TestUnsupportedDialect, …).

   Remainder (2 items), routed as task 2486 (queue repo-health-nix-pilot, dedupe repo-health:v1:fix:dezren39/nix:issue:254):

   1. The matrix still marks json-schema-document-dialects as **gap** #254: no document states which dialects mcpx supports (conformance-matrix.md:1382 and :2070) — stale: docs/schema-validation.md states the dialect policy in full. Update both rows.
   2. Record/implement the structuredContent output policy explicitly (warn-only with rationale, or enforce) in docs/schema-validation.md and on this issue.

   Only those two items keep this issue open; do not re-implement the validator.
3. dezren39

   added

   kind/bugSomething isn't working (prefixed form of the classic bug label)Something isn't working (prefixed form of the classic bug label)

   priority/lowNice to have; do when convenientNice to have; do when convenient

   effort/lLarge: multi-day or open-ended; expect staged check-insLarge: multi-day or open-ended; expect staged check-ins

   meta/enrichedIntake review done: acceptance criteria, links, and normalized labels addedIntake review done: acceptance criteria, links, and normalized labels added

   app/mcpxPackage/app: mcpx (pkgs/ or apps/ in this repo)Package/app: mcpx (pkgs/ or apps/ in this repo)

   queue/queuedHas a queued task in the Supabase agent queueHas a queued task in the Supabase agent queue

   status/needs-triageNot yet triaged; needs a first lookNot yet triaged; needs a first look

   work/assignedQueue worker lifecycle stateQueue worker lifecycle state

   queue/claimedQueue worker lifecycle stateQueue worker lifecycle state

   status/in-progressQueue worker lifecycle stateQueue worker lifecycle state

   and removed

   status/needs-triageNot yet triaged; needs a first lookNot yet triaged; needs a first look

   queue/queuedHas a queued task in the Supabase agent queueHas a queued task in the Supabase agent queue

   on Oct 28, 2026
4. dezren39 commented on Oct 28, 2026

   

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   🤖 Agent note · picked up

   • Agent: queue worker (repo-worker-code), Lane A shift
   • Session / ID: queue task 2849
   • Found via: queue claim
   • Task: Triage relocated issue mcpx: JSON Schema validation of tool inputs/outputs and elicitation schemas (7 conformance rows) #1951 — dedupe against existing code issues, confirm scope against current pkgs/mcpx on main, enqueue implementation follow-up (no implementation in this triage task)
   • Expectation: effort s — done = triage verdict posted, follow-up enqueued or duplicate closed with pointer
   • Links: queue task 2849
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6. dezren39 commented on Oct 29, 2026

   

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   🤖 Agent note · parked

   • Agent: queue worker (repo-worker-code), lane B shift
   • Session / ID: queue task 2875
   • Found via: queue claim (resume from awaiting_ci)
   • Task: Parked on ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 again, with fresh evidence: PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 is merge-ready (mergeState CLEAN, all reported checks pass, Codex review of head 16c54b1 completed with no findings), but its merge-queue entry — enqueued this shift, position 1, AWAITING_CHECKS — was ejected after ~2 minutes (mergeQueueEntry null, PR still OPEN), exactly the ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 pattern. Datapoint posted on ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403.
   • Expectation: Resume when ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 is fixed/closed: re-enqueue PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190, confirm it merges, then close mcpx: JSON Schema validation of tool inputs/outputs and elicitation schemas (7 conformance rows) #1951 and complete this task.
   • Links: PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 · blocker ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403
7. dezren39

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   queue/parkedQueue task is parked (waiting on CI, time, or an event)Queue task is parked (waiting on CI, time, or an event)

   status/parkedDeliberately paused with a recorded resume conditionDeliberately paused with a recorded resume condition

   and removed

   status/in-progressQueue worker lifecycle stateQueue worker lifecycle state

   queue/claimedQueue worker lifecycle stateQueue worker lifecycle state

   on Oct 29, 2026
8. dezren39 commented on Oct 29, 2026

   

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   🤖 Agent note · parked

   • Agent: queue worker (repo-worker-code), lane B shift
   • Session / ID: queue task 2875 (second claim this shift)
   • Found via: queue claim — the 20-minute park from my earlier claim this shift expired and the task recirculated unchanged.
   • Task: Nothing has changed since the park 20 minutes ago: main is still 5a34fa70, ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 is still open, and PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 is still OPEN / CLEAN and merge-ready. Re-parking with a 1-hour delay so the task stops recirculating while the merge-queue stall persists; the resume condition is unchanged.
   • Expectation: Resume when ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 is fixed/closed: re-enqueue PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190, confirm it merges, then close mcpx: JSON Schema validation of tool inputs/outputs and elicitation schemas (7 conformance rows) #1951 and complete this task.
   • Links: PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 · blocker ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403
9. dezren39

   added

   queue/blockedQueue or user escalation stateQueue or user escalation state

   status/blockedQueue or user escalation stateQueue or user escalation state

   user/escalatedQueue or user escalation stateQueue or user escalation state

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   status/parkedDeliberately paused with a recorded resume conditionDeliberately paused with a recorded resume condition

   queue/parkedQueue task is parked (waiting on CI, time, or an event)Queue task is parked (waiting on CI, time, or an event)

   work/assignedQueue worker lifecycle stateQueue worker lifecycle state

   on Oct 29, 2026
10. dezren39 commented on Oct 29, 2026

    

    dezren39

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    🤖 Agent note · implementation complete, blocked only on the repo-wide merge-queue freeze (#2403)

    • Agent: queue worker repo-worker-code, OpenChamber scheduled lane. Task 2875 (claim), escalated to you after three park cycles.

    • Work is done and verified. PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 — queue/2875-1951-schema-dialect-remainder, OPEN / CLEAN / MERGEABLE, all reported checks green (basic: proxy port fallbacks SUCCESS, mcpx conformance basic: spec parity SUCCESS, mcpx basic: test SUCCESS, CodeRabbit neutral). Five files, matching the packet's two items plus the third-row check:

      • docs/spec/conformance-matrix.md — both json-schema-document-dialects rows (was :1382 / :2070) no longer read **gap** #254; they cite the tests that pin the documented dialect set. The json-schema-bound-composition-cost row (n/a: no validator) was also stale and now cites schemaval.TestSchemaTooLarge (the 1 MiB MaxSchemaBytes bound).
      • docs/spec/requirements.md — the two catalogue rows updated to match (matrix is generated from these).
      • internal/conformance/coverage_messages.go — the Server and Client Gap registrations for both IDs removed, replaced by coverage entries with the reason in comments.
      • docs/schema-validation.md — new "Output policy: structuredContent is warn-only" section: inputs enforced (-32602), outputs validated by checkToolOutput but delivered unchanged with a Warning, the rationale (mcpx is a gateway for schemas it does not own), and the design(mcpx): JSON Schema validation of tool input and output — one validator at the client choke point #1481 / mcpx: Phase 2 of #1481 — validate tool arguments at CallTool (enforce, -32602) + structuredContent against outputSchema (warn-only) #1483 pointers, with an explicit statement that flipping to enforcing is a separate decision.

    • Nothing left to implement. The validator was not touched, elicitation (Phase 3 / mcpx: Phase 3 of #1481 — validate elicitation form answers against requestedSchema in client.answer #1484) not touched, dezren39/nix not touched.

    • Why it is not merged: ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403. main has not moved since 5a34fa7 (10:57:51Z, ~11 h); every merge-queue entry is ejected with reason=branch_protection_failure within 24–51 s of its required check going green. Ruleset 26115813 has bypass_actors: [], and main's classic protection carries a push restrictions block (users: [], teams: [codeowners], apps: [github-actions]) that the merge group cannot satisfy. This is not a PR defect and not something a worker can change.

    • Your decision (one of two config changes): (a) drop the classic push restrictions on main (or add the merge-queue actor to them), or (b) move the required check basic: proxy port fallbacks into ruleset 26115813. Either unblocks mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 and the other ~15 CLEAN PRs parked on the same condition.

    • Resume condition: the first PR that merges through the queue → re-enqueue mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190, merge, close this issue. Task 2875 is blocked (escalated-to-user), not parked, so it stops recirculating in the worker pool.

    • Links: PR mcpx: close #1951 remainder — stale dialect-gap rows + structuredContent warn-only policy doc #2190 · ci: merge queue ejects every PR — no merge since #2233 (10:57Z), entries dropped 2-6 min into AWAITING_CHECKS #2403 · task 2875
11. dezren39

    closed this as completedin #2190on Oct 30, 2026
12. dezren39

    added a commit that references this issue on Oct 30, 2026

    Merge pull request #2659 from developing-today/docs/roadmap-sync-json…

    ...

    4b48bf1