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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true, destructiveHint=false). The description adds almost nothing beyond what annotations provide — 'authenticated router' is a vague claim that doesn't specify auth mechanism or requirements. No mention of rate limits, data freshness, unit specifics, or provenance format despite claiming to return both.

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?

The description is very short but not in a good way — it is under-specified rather than concise, with trailing whitespace and no front-loaded functional explanation. Every word present does little work.

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?

A read-only hydrology data tool with 4 params, 0% schema coverage, no output schema, and no annotations that explain data semantics. The description provides nothing about what data is returned, units, site_id format, date semantics, or the meaning of the parameter_code enum. Completely inadequate.

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% across 4 parameters, so the description must fully compensate. Instead it says nothing about site_id format, the date range semantics for start/end, or what the parameter_code enum values (00060, 00065, 00010) mean. The description completely fails its parameter-documentation burden.

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?

The description only identifies the router and tool name ('usgs_daily') without stating what the tool does in functional terms. It mentions 'Returns normalised SI data and source provenance', which hints at a data retrieval purpose, but 'usgs_daily' is opaque and the description never explains that it fetches daily USGS hydrological time-series data. It does contextually distinguish from siblings like nrfa_get_timeseries or ea_hydro_series via the USGS provenance, but barely.

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?

No usage guidance whatsoever. The description does not say when to use this tool versus siblings like nrfa_get_timeseries, ea_hydro_series, or rainfall_latest. No prerequisites, no exclusions, no routing logic beyond the opaque tool name.

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