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

Annotations already cover read-only, idempotent, open-world and non-destructive behavior, so the description only needs to add context — and it does: the return is raw image bytes through MCP (not JSON), it includes source timestamp metadata, and it will not yield a still for video-only cameras. It stops short of disclosing size limits, latency, or failure modes for unavailable cameras.

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?

Four short sentences, each load-bearing, with the core action front-loaded and the prerequisite and edge case following in priority order. No filler or restatement of the title.

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?

No output schema exists, and the description compensates by stating what comes back (image bytes plus timestamp metadata) and when it won't (video-only cameras). Combined with annotations covering the safety profile and the schema covering the ID pattern, an agent has everything needed to call this 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 description coverage is 0%, so the description carries the burden for camId and largely does: it tells the agent the ID must come from list_cams and be filtered to snapshotAvailable=true. The lowercase/dash pattern is only in the schema and the description doesn't restate it, but the value-source constraint is the more important semantic.

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+resource ('Fetch a public camera JPEG') plus the payload characteristic (source timestamp metadata), which separates it cleanly from sibling list_cams and the many get_* environmental tools. An agent knows immediately this returns a still image, not conditions data.

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 an explicit prerequisite workflow ('First use list_cams and request only IDs with snapshotAvailable=true') and an explicit exclusion/alternative ('Video-only cameras provide a liveUrl instead of a still'). Both the when and the when-not are stated, leaving nothing to inference.

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