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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering safety and determinism. The description goes beyond by disclosing output contents (count, per-locus verdicts, GvH/HvG mismatch counts, flags) and a critical edge-case behavior: unresolvable typing yields 'potential', never a confident count. This adds real behavioral context not present in annotations.

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 a single dense paragraph that front-loads the core action and method, then packs in input format, framework, output summary, and an edge case. Every sentence adds value; no fluff or redundancy. It is well-structured for quick parsing.

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 tool's moderate complexity (nested objects, 3 params) and the presence of an output schema, the description covers input format, framework choices, output summary, and the key edge case of unresolvable typing. The only minor gap is the inconsistency between 'two reported alleles per locus' in the description and 'up to 4' in the schema, which could cause slight confusion but does not undermine overall completeness.

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 67% (recipient and donor described, framework only enum). The description adds meaningful semantics: it gives a concrete example format, states 'two reported alleles per locus' and 'any nomenclature era', and reinforces the privacy constraint (allele strings only). This goes beyond the schema's brief descriptions, though the framework parameter is still only enumerated.

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 states a specific action ('Count a donor-recipient HLA match'), a precise method ('published counting rules R1-R6'), and explicitly differentiates from a sibling ('not a donor recommendation'). It also clarifies the computation domain ('allele arithmetic over chromosomes'), leaving no ambiguity about what the tool does.

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 description implies usage by specifying the input format and framework, and it excludes one alternative use case ('not a donor recommendation'), which hints at when not to use it. However, it does not explicitly name alternatives like check_typing or donor_compat or state conditions for choosing them. Still, the context is clear enough for an agent to infer basic selection.

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