camera_snapshot

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

Annotations already declare it safe, idempotent and read-only, so the description's value is in the extra behavior it discloses: images wider than the policy's max_image_width are downscaled, and the call is refused outright if Pillow is unavailable. That is a genuinely non-obvious failure mode an agent could not infer from the schema or annotations.

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 short sentences, front-loaded with the action, then the return shape, then the size caveat. No filler and every sentence carries information the agent needs.

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?

There is no output schema, and the description compensates by describing the return as an image plus JSON metadata (width, height, stamp). Combined with the downscale/refusal caveat, an agent knows what it will get and what can go wrong; only the behavior on a stale or unavailable topic is unstated.

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 0%, so the description must carry the parameter meaning, and it does: 'topic' is constrained to an allowlisted camera topic and the agent is told exactly where to look it up (get_safety_envelope.camera_topics). It doesn't specify the string format of a topic name, which would have earned a 5.

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?

States a specific verb and resource ('Grab the latest image from an allowlisted camera topic') and clarifies the scope constraint (allowlist). No sibling tool fetches camera imagery, and the description points to get_safety_envelope for valid topics, so an agent can place it precisely.

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?

Gives clear context for use by naming the prerequisite — the topic must come from the allowlist returned by get_safety_envelope.camera_topics. It doesn't state when not to use it or name an alternative, but for a read-only snapshot there is no competing sibling.

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