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

Annotations already cover readOnly/openWorld/destructive/idempotent, and the description adds real value beyond them: anonymous rate limits (60/hr, 300/day), no-key/no-signup auth, SI normalisation, provenance, and OGL licence warnings. It stops short of describing return structure or pagination, keeping it out of the 5 range.

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?

Purpose and the safety caveat are front-loaded well, but the definition pads with 'TerraMCP is a Wrench AI service' and repeats licence/quota language. The useful content (scope, limits, SI) is buried among marketing 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 4-param, no-output-schema query tool with annotations, this covers scope, auth, rate limits, and licence adequately. The only gap is that the actual shape of the 'bounded metadata' returned is not hinted at, though no output schema exists to describe it.

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% and each parameter (lat, lon, limit, radius_km) is documented with bounds and defaults in the schema. The description adds nothing about parameter syntax or units beyond the schema, so baseline 3 applies.

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), resource (Environment Agency water-quality sampling points), and scope (near a WGS84 point, England). Combined with the explicit 'not a water-safety assessment' note, an agent can distinguish it from siblings like wq_measurements and ea_groundwater_stations.

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 useful context ('near a WGS84 point', returns metadata not an assessment), but never names an alternative or states when-not to use it. The sibling wq_measurements is the obvious complement and goes unmentioned, so routing is left to inference.

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