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

Annotations declare readOnly, openWorld, non-destructive, non-idempotent. The description adds that it is an authenticated router and returns normalised SI data plus source provenance, which is useful auth and return context. It does not contradict annotations and adds value beyond them.

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 router/auth and return info before the purpose. No wasted words, though the first sentence partly restates the tool name. Efficient overall.

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?

Given a 4-parameter spatial tool with no output schema, the description covers purpose, auth, and return nature but omits parameter semantics, pagination, and sibling alternatives. It is partially complete but leaves gaps an agent must resolve from the schema.

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% for all 4 parameters; the description only says 'nearby' and parameter=rainfall, adding no meaning for lat, lon, limit, or radius_km. Parameter names and schema constraints help, but the description fails to compensate for the undocumented parameters.

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 ('Find') and resource ('EA rainfall stations'), with scope 'nearby' and parameter=rainfall. It implicitly distinguishes from rainfall_latest and flood_find_stations but does not name siblings explicitly. Clear enough for selection.

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?

Provides no explicit when-to-use or when-not-to-use guidance, nor alternatives among siblings like rainfall_latest or flood_find_stations. 'Find nearby' implies a spatial lookup but leaves the agent to infer context. No prerequisites stated beyond authentication in the prefix.

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