Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds useful behavioral context beyond annotations by explaining that the tool surfaces available axes and distinguishes required vs optional postcoordination. No contradiction with annotations exists.

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 description is concise and front-loaded with the core action, followed by a scannable bullet list of use cases. The final conceptual sentence about postcoordination adds helpful domain context without much redundancy.

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?

Given the single required parameter, full schema coverage, existing output schema, and strong annotations, the description is sufficiently complete for an agent to understand when and why to invoke this tool. Minor gaps like code format examples or explicit exclusions are not critical here.

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?

The schema already fully documents the single 'code' parameter with 100% coverage. The description only repeats that it applies to an ICD-11 code, adding no format, validation, or syntax details beyond what the schema provides, so the baseline score of 3 is appropriate.

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?

The description opens with a specific verb and resource: 'Get postcoordination information for an ICD-11 code.' This clearly identifies what the tool does and differentiates it from siblings like icd11_lookup, icd11_hierarchy, and icd11_search, none of which focus on postcoordination axes.

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?

The 'Use this tool to' section provides concrete use cases: finding axes, checking required vs optional postcoordination, and understanding extension possibilities. It gives clear context for when to call the tool, though it does not explicitly state when not to use it or name alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.