List capture devices

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

The readOnlyHint annotation already establishes safe read behavior. The description adds non-obvious behavioral details: each entry supplies a device_id and source_type for direct use in add_source, and displays include is_primary and resolution. This goes beyond the schema to explain output shape, though it doesn't discuss potential edge cases or errors.

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, front-loaded with the core action, then output details, then an example use case. No redundant phrases; every sentence adds value. The categories in the first sentence align with the enum without being wasteful.

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 read-only listing tool with one optional param and no output schema, the description fully covers the purpose, the returned fields, and the intended workflow (call first, pass to add_source). The readOnlyHint annotation handles safety, and the tool's simplicity doesn't require more.

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 already has 100% coverage of the single 'kind' parameter, with a description 'Filter to one device kind.' The description enumerates the kinds in its opening sentence but doesn't explicitly connect them to the parameter's filtering role beyond that. This matches the baseline of 3 for high schema coverage.

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 opens with 'Enumerate capture devices available to add as sources' – a specific verb+resource that clearly differs from sibling list_sources (which likely lists existing sources). It enumerates the device categories and notes the output feeds add_source, anchoring its purpose in the tool ecosystem.

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?

It provides explicit usage context: 'Call this first to find, e.g., the user's webcam or primary monitor' and notes the results are 'ready to pass straight to add_source.' However, it doesn't explicitly state when not to use it or name alternatives like list_sources, so it falls short of a 5.

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