canimcp

canimcp digest

Checked 10 tools (corpus 2026.10.16).

Per-client verdict

• codex: 1 error, 5 warn
• claude-code: 2 warn
• client-independent: 2 finding(s)

Findings, ranked

[error] root oneOf/anyOf next to properties (codex 0.162.0, evidence: probe)
tool: create_payment, path: inputSchema
A root oneOf or anyOf placed next to "properties" made Codex lose the property names - the call reached the server with mangled arguments. r/mcp reports a production tool silently dropped 17 days over a root oneOf.
fix: move the composition inside each property, or wrap the object so "properties" is not a sibling of oneOf/anyOf

[warn] prefixItems tuple in inputSchema (codex 0.162.0, evidence: probe)
tool: batch_insert, path: inputSchema
A prefixItems tuple was declared to the model as Array<string> - the per-position types were erased.
fix: model the arguments as an object with named properties instead of a positional tuple

[warn] integer argument that can exceed 2^53 (claude-code 2.1.295, codex 0.162.0, evidence: probe)
tool: search_events, path: inputSchema.properties.since
int64 value 1234567890123456789 arrived rounded on Claude Code, and string-or-rounded on Codex.
fix: accept big integers as strings and parse on the server

[warn] integer argument that can exceed 2^53 (claude-code 2.1.295, codex 0.162.0, evidence: probe)
tool: search_events, path: inputSchema.properties.until
int64 value 1234567890123456789 arrived rounded on Claude Code, and string-or-rounded on Codex.
fix: accept big integers as strings and parse on the server

[warn] inputSchema over ~14 KB (codex 0.162.0, evidence: measured)
tool: sync_catalog, path: inputSchema
Codex compacts large input schemas to fit a per-server budget (~20 KB). A 14 KB schema lost its required nested fields and calls arrived incomplete (0/3).
fix: shrink the schema (shared $defs help), or raise Codex's per-server schema budget to 20000 if you control the client

[warn] enum inside anyOf/oneOf in a >5 KB schema (codex 0.162.0, evidence: probe)
tool: sync_catalog, path: inputSchema
An enum nested inside anyOf in a schema over 5 KB had the enum erased by Codex's schema compaction - the model no longer saw the allowed values.
fix: hoist the enum to the property root, or shrink the schema under ~5 KB

[advisory] tool name over 64 chars or non-ASCII charset (all clients, evidence: historical)
tool: fetch.page, path: name
Some clients have silently truncated or rejected long/unusual tool names. A 65-char name worked on Claude Code 2.1.287 and Codex 0.162.0, but older or enterprise-pinned clients may still drop it.
fix: keep names under 64 chars, [A-Za-z0-9_-] only

[advisory] tool name over 64 chars or non-ASCII charset (all clients, evidence: historical)
tool: generate_report_for_customer_account_with_full_history_and_exports, path: name
Some clients have silently truncated or rejected long/unusual tool names. A 65-char name worked on Claude Code 2.1.287 and Codex 0.162.0, but older or enterprise-pinned clients may still drop it.
fix: keep names under 64 chars, [A-Za-z0-9_-] only

Advisories (always-on behaviors worth knowing)

• (codex 0.162.0) After a server's tool list changed, Codex kept using its old catalog and never called the new tool (0/3). Fix: restart the client session after deploying new tools
• (codex 0.162.0) With gpt-5.6-sol, Codex runs in code mode: the model never sees your JSON Schema, only a compacted TypeScript declaration generated from it - several Codex failures happen in that translation. Fix: assume the client sees a lossy projection of your schema, not the schema itself

Static analysis only: this checks schemas against a quirks corpus. It cannot see runtime result shapes or a client build newer than the corpus (2026.10.16).