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

Beyond the readOnly and idempotent annotations, the description clearly discloses important runtime behavior: an unresolved feature returns found: false with guidance rather than throwing an error, and the response echoes which identifier form matched. This tells the agent what to expect on both success and miss paths.

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 cover the output contents, accepted input forms, and error-like miss behavior in a front-loaded order. There is no filler or repetition of schema details; every sentence earns its place.

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?

The description is complete for a read-only single-feature lookup tool: it states the return contents, input conventions, example identifiers, and unresolved-key behavior. Parameter semantics are fully covered by the input schema, and return structure is covered by the output schema, so nothing needed to call the tool correctly 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?

Input schema coverage is 100%, so the schema already documents the parameters. The description adds real value on top by explaining accepted identifier formats (BCD key vs web-features id) with concrete examples and noting that the response echoes which one matched. This helps an agent construct the feature argument correctly.

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 names a specific verb and resource ('Get the compatibility record for one web feature') and enumerates exactly what the record contains. It does not explicitly differentiate itself from the sibling tools such as browsercompat_check_baseline or browsercompat_compare_support, but the singular 'one web feature' scope makes the core purpose unmistakable.

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 when to use it: when you need a full compatibility record for a single web feature. It also gives behavioral context about unresolved keys and accepted identifier forms, but it never explicitly says when not to use it or names alternatives like browsercompat_compare_support or browsercompat_list_reference.

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