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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint=false), so the description earns credit for adding real behavioral context: 'unresolvable typing yields potential, never a confident count' tells the agent how ambiguous input is handled. It also discloses return contents, though an output schema 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?

Front-loads the core action and the key caveat before detailing input shape and return values. It is dense and slightly run-on across the framework and return sentences, but every clause carries information and nothing is redundant.

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 complex tool with nested objects, an output schema, and rich annotations, the description is largely complete: it covers input format, framework choices, the R1-R6 rule basis, and the ambiguous-input fallback. Minor gaps remain around ordering/dominance of rules and what the flags specifically mean, but the essentials for correct invocation are present.

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?

With 67% schema coverage the schema documents recipient/donor and the framework enum, but the description meaningfully extends this: two reported alleles per locus, tolerance across nomenclature eras including G/P group names, and allele-strings-only constraint. This adds syntax and format detail beyond what the schema states.

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 and resource (count a donor-recipient HLA match) and pins the method to the published R1-R6 rules. Crucially, it distinguishes itself from the sibling donor_compat by declaring it is 'allele arithmetic... not a donor recommendation', so an agent can route correctly without opening schemas.

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?

Clearly frames the use context (counting by published rules, not recommending a donor) and names acceptable framework values, which helps the agent choose this over donor_compat. However, it does not name specific alternatives (e.g., check_typing, validate_gl_string) or state explicit when-not conditions beyond the single scope exclusion.

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