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

Annotations establish read-only, idempotent, closed-world behavior, and the description adds non-obvious behavior beyond them: counts are always complete while each list is capped by `limit`, and `truncated` signals that cap. It also discloses that deletions carry a reason and successor, which shapes how results should be interpreted. No permission or rate-limit detail, so not a 5.

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?

Three sentences, front-loaded with what is diffed, then the truncation contract, then the motivating use case. No filler and no repetition of the tool name or title.

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?

An output schema exists, so return values need no prose. The description supplies the operational facts an agent needs: scope of the diff, truncation semantics, and the purpose that selects this tool over siblings.

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% and the schema already documents release format, locus, and the limit default, so the baseline is 3. The description goes further by explaining the interaction between `limit` and the `truncated` flag and clarifying that counts are unaffected by truncation, which the schema does not say.

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?

States a specific verb set (added, removed, renamed) on a specific resource (HLA allele names) across two named releases, with an optional locus scope. It is immediately distinguishable from siblings like allele_history or allele_info, which deal with individual alleles rather than a release-to-release diff.

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?

Gives a concrete use case ('see what a release update changes before re-running or re-reporting typings'), which tells the agent when this tool belongs in a workflow. It stops short of naming an explicit alternative or stating when not to use it, so it lands at 4 rather than 5.

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