list_capabilities

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

With no annotations provided, the description carries the full burden. It discloses a key behavioral trait: 'A capability existing does not mean verified endpoints are available for it.' It does not list other traits like rate limits or pagination, but the scope is appropriately limited for a listing tool.

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 sentences, all essential. The first sentence states the purpose, the second gives usage context, and the third adds a critical caveat. No wasted words.

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 low complexity (no required parameters, no output schema, no nested objects), the description covers the main points: purpose, filtering, and the important caveat about live endpoints. It's complete enough for an agent to use correctly.

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 100%, so the description doesn't need to re-document parameters. It provides context about how to use the parameters ('filter by tag' and 'search by keyword'), which adds some value beyond the schema's descriptions. The baseline of 3 is appropriate.

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 purpose: 'List available API capability types.' It names the resource ('capability types') and the action ('list'). The context about filtering and searching further clarifies its function, and the note distinguishes it from sibling tools like discover_paid_api.

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 explicitly says when to use this tool ('explore what kinds of APIs are available in the registry') and how to filter. It also provides clear guidance on when NOT to rely solely on this tool, directing users to 'discover_paid_api to check for live endpoints.' This helps the agent choose between siblings.

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