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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the description doesn't need to restate those. It adds valuable behavioral context: the biological mechanism (silent recombination), the ordering of results 'by repeat length and spacer', and a key limitation ('Reports no deletion RATE'). This goes beyond the structured annotations and helps the agent understand what to expect from the tool's output.

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 five sentences, each serving a distinct purpose: purpose, biological context, output specifics, limitation, and workflow recommendation. It is front-loaded with the main function and stays under ~120 words without fluff or repetition. This is appropriately concise for the tool's complexity.

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?

With no output schema, the description explains the return format ('coordinates plus the resulting sequence(s)') and the ordering. It also provides context about the biological significance and next-step validation. The schema covers parameter details like defaults and circular behavior, so the description doesn't need to repeat those. It is complete enough for effective use, though it doesn't explicitly mention the pairsFound field (which is in the schema for maxPairs).

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 has 100% coverage for all 5 parameters, so the baseline is 3. The description adds extra meaning by explaining the sorting logic ('ordered by repeat length and spacer') which directly relates to maxPairs and minRepeatLength. It also mentions circular behavior implicitly through 'each pair would collapse to', complementing the schema's detailed description of circular. This enriches the parameter semantics beyond the schema.

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 clearly states the tool's function: 'Find the exact direct repeats in a construct that make it deletable, and build the molecule each pair would collapse to.' The verb 'Find' and resource 'construct' are specific, and the title 'Repeat instability (what the construct can delete)' further clarifies the purpose. It distinguishes itself from siblings like diagnostic_digest by describing the predictive nature of the tool and suggesting a downstream validation step.

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 provides clear usage context: it explains the tool identifies deletable repeats and mentions a specific workflow ('Feed a deletion product to diagnostic_digest to screen for it'). It also sets expectations by stating 'Reports no deletion RATE: none is derivable from sequence alone', which excludes a potential misuse. However, it does not explicitly say when to avoid this tool in favor of alternatives beyond diagnostic_digest.

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