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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: the server often does not ship historical snapshots, bundled_versions is the source of what is actually available, and this tool intentionally returns guidance rather than computed diffs. That goes beyond what annotations alone convey.

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 longer than average but each section earns its place: the general guidance rule, the ICD-10/11 special case, the parameter behavior, and the closing caveat all contribute distinct information. It is well structured and front-loaded with the core purpose; minor redundancy exists between the early 'guidance only' statement and the closing changelog-authoritative caution.

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?

For a metadata/guidance tool with an output schema present, the description is complete: it covers the general behavior, the notable exception, exactly how to invoke the special case, and what information will be returned. No critical operational detail is missing.

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 coverage is 100%, so the schema already documents each parameter at a basic level. The description adds real value above that by explaining the consequence of omitting from_version and to_version and by specifying the special icd10/no-to_version invocation for the cross-revision summary. This is more than the schema alone provides.

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 precise verb and resource: 'Report what diff data is available between two versions of a terminology.' It then distinguishes itself from actual diff or mapping tools by calling itself 'a metadata + guidance layer, not a diff engine,' and it names the special ICD-10 vs ICD-11 behavior, making it easy to separate from siblings like map_icd10_to_icd11.

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?

Explicit guidance is given for when this tool is appropriate: most terminologies get guidance-only changelog info, while ICD-10 vs ICD-11 gets a real cross-revision summary. The description also tells the agent exactly how to trigger that case ('Use terminology: "icd10" with no to_version') and warns that for frequently changing terminologies the publisher changelog is authoritative.

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