EVERY ERROR THIS API CAN RETURN, documented before you hit it: cause, family, whether retrying helps, and what to do instead. Includes the JSON-RPC codes and the idempotency contract. Use this to write error handling that branches on codes rather than on message text. NEXT: hello to start working.
| Name | Required | Description | Default |
|---|---|---|---|
| code | No | A single error code to look up. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, matching a static local reference set. The description usefully adds that retry semantics and the idempotency contract are included, which is real behavioral context beyond the annotations, but it says nothing about the shape or size of the payload or how the optional code lookup changes behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The content list is front-loaded in a single dense clause and each sentence carries information. The trailing 'NEXT: hello to start working' is cross-promotion for a sibling tool and doesn't earn its place in this tool's definition.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description must carry the return-value burden and does so by naming the fields returned (cause, family, retryability, remediation, JSON-RPC codes, idempotency contract). It is nearly complete for a static read reference, missing only how the optional code filter alters the response.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the single optional 'code' parameter is already documented in the schema. The description implies the default no-argument call returns the full catalog ('EVERY ERROR') and that per-code lookup is possible, but adds no detail on format or behavior when code is omitted. Baseline 3.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
'EVERY ERROR THIS API CAN RETURN, documented before you hit it' states the resource and scope precisely, and the enumeration (cause, family, retryability, remediation, JSON-RPC codes, idempotency contract) makes clear exactly what the catalog contains. No sibling tool covers error semantics, so no differentiation is needed.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
'Use this to write error handling that branches on codes rather than on message text' gives a concrete context for invoking it, and 'NEXT: hello to start working' sequences it in the workflow. It lacks an explicit when-not or a statement about whether to call it once vs. per-code, so it stops short of a 5.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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