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

Goes well beyond the annotations (readOnly/openWorld/non-destructive) by disclosing anonymous rate limits (60/hour, 300/day per IP and session), the no-API-key open-data model, quota fallback behavior, SI normalisation of hydrological units, provenance in the response, and the interpretative caveat about bbox vs. point conditions. This is exactly the operational context annotations cannot carry.

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 purpose and the key caveat are front-loaded in the first two sentences, which is the right ordering. It is dense but mostly earns its place, with only mild promotional filler ('TerraMCP is a Wrench AI service') that could be trimmed.

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 carries the return-value burden and does so reasonably ('bounded properties and geometry summaries', source data and provenance). Combined with the rate limits and the bbox-vs-point caveat, an agent has enough to call and interpret it, though field-level detail on the returned properties is absent.

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 the baseline is 3. The description reinforces the bbox semantics of radius_km and the 10 km cap and points at bgs_collections for collection values, but these largely restate what the schema already documents, adding little new parameter-level meaning.

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 (query), a specific resource (BGS borehole index / geology 625k features), and the spatial scope (features intersecting a WGS84 bounding box around a UK point, up to 10 km). The named collection set makes it clearly distinct from siblings like bgs_collections (which lists collections) or the EA/flood spatial tools.

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 clear context for use (spatial proximity query in the UK, radius capped at 10 km) and implicitly routes the agent to bgs_collections for the collection identifier. It also supplies an important interpretive exclusion — bbox matches do not establish conditions at the exact point — but names no explicit alternative tool when a point-exact answer is needed.

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