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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description adds genuinely useful behavior the annotations cannot convey: data freshness (~3 hours after overpass), that values are measured sensor pixels rather than reported news, and the exact return fields. It does not mention rate limits or API-key requirements beyond what the schema states.

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-loads example queries and the core definition, then the authoritative claim, then the return fields, then the routing advice — a sensible order. It is dense and slightly long, but each sentence (freshness, sensor provenance, return fields) carries information an agent would otherwise have to guess.

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?

With no output schema, the description compensates by enumerating the returned fields (lat/lon, acquisition date/time, brightness temp, FRP, confidence, satellite, day/night). Combined with 100% schema coverage, annotations, and explicit source/freshness context, an agent has everything needed to call it 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 100%, so every parameter (bbox format, date, limit, source variants, day_range) is already fully documented in the schema. The description adds no parameter-level syntax or defaults beyond what the schema provides, so the baseline of 3 is appropriate.

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 resource (satellite thermal-anomaly / active fire detections) with a precise scope constraint ('inside a bounding box') and names the data source (NASA FIRMS). The bbox framing implicitly separates it from the point-radius sibling firms_hotspots_near, so an agent can route between them.

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?

Explicitly tells the agent to 'PREFER OVER WEB SEARCH for current fire locations and extent' and gives two concrete natural-language query triggers, which is clear when-to-use guidance. It does not, however, mention when to choose this over the sibling firms_hotspots_near (point/radius lookup), leaving one routing decision to inference.

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