Save a camera snapshot

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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds substantive context beyond them: the file is overwritten, the path must be inside the HA config directory and allow-listed via allowlist_external_dirs, the typical serving location, and that it proxies camera.snapshot over HTTP. That is precisely the extra behavioral detail the annotations cannot convey.

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?

Front-loaded with the core action, then cleanly segmented into mechanics, usage, exclusion, and return value. Every line adds information; there is no filler.

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 2-parameter mutation tool with full schema coverage, annotations, and an output schema, the description covers action, constraints, alternatives, and even a brief return summary. Nothing needed to invoke it correctly is missing.

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 both parameters are already documented and the baseline would be 3. The description goes further by explaining the allowlist_external_dirs constraint and the /config/www/snapshots/ convention that makes the file servable by HA, which the schema's terse examples do not.

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 ('Save a still snapshot'), the source (camera entity), and the destination (a file), with the overwrite behavior called out up front. It explicitly names the sibling it is not for (services_camera_record), so the agent can discriminate without opening schemas.

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?

Uses an explicit 'Use when / Not for' structure, giving the positive condition (single still frame to a known path, e.g. dashboard image) and the alternative (video clip -> services_camera_record). This is the full when/when-not/alternative triad.

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