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

Beyond the annotations, the description explains the meaning of 'supported' (bounded, read-only OpenSearch query succeeded for this exact account generation), clarifies that it does not mean the index contains messages or covers the mailbox, and warns against fallback to live provider search. This is rich behavioral context that materially helps an agent interpret results correctly.

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 three tightly written sentences, front-loaded with the tool's purpose, then defining key status semantics and constraints. Every sentence earns its place with no redundancy.

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 simple one-parameter capability-check tool with no output schema, the description does a good job explaining return statuses, interpretation caveats, and constraints. It could be slightly more complete by noting how to source the accountId or its explicit relationship to sibling search tools, but it is largely sufficient.

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 0% description coverage for the single accountId parameter. The description adds some meaning by saying it targets 'one mailbox' and 'this exact account generation,' but it does not explain the expected ID format or where to retrieve a valid accountId, leaving a gap even for a one-parameter tool.

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 verb and resource: 'Check cache-only recipient-search capability for one mailbox.' It clearly distinguishes a capability check from an actual search operation, though it does not explicitly name the sibling search tool it relates to.

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 some usage guidance: 'pending' should be retried later and unsupported scopes must not fall back to a live provider search. However, it does not explicitly say when to call this tool versus search_cached_threads_by_recipient or how to obtain the accountId.

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