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

Annotations indicate a mutating, idempotent, non-destructive operation. The description adds behavioral detail: it returns the project identity with the result, and it is project-scoped, meaning it affects only the specified project. It also explains the '0 clears' behavior, which is a meaningful semantic detail. It does not mention auth or rate limits, but with annotations covering safety, the added context is sufficient for a 4.

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 with zero wasted words. It front-loads the critical project-scoping constraint, then states the functional behavior, and ends with a concrete example. Every sentence earns its place, making it easy to parse and act on.

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 tool with only 3 parameters, no output schema, and clear annotations, this description is complete. It explains the scoping rule, the parameter units and semantics, the clearing behavior, and the return value (project identity). An agent has everything needed to invoke it correctly without additional inference.

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 only 33% (only project_id is described), so the description carries the burden for the fade parameters. It explains that fade_in_s and fade_out_s are in seconds, that 0 clears the fade, and provides a concrete example. This fully compensates for the missing schema descriptions and adds semantic clarity beyond the raw number types.

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: setting fade-in and fade-out durations for video and audio. It specifies the verb 'Fade', the resource (the project), and the exact behavior (start and/or end, seconds, 0 clears). It is distinct from sibling tools like set_transitions or set_speed, which handle different effects, so an agent can easily differentiate it.

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 explicitly states the call is project-scoped and requires an explicit project_id, and explains the units and clearing behavior. It does not explicitly list alternative tools or when not to use it, but the function is self-explanatory for fade tasks. The lack of exclusions is a minor gap, so 4 is appropriate.

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