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

Annotations already declare read-only, non-destructive, open-world behaviour, and the description adds real value beyond them: license (OGL v3), the names-vs-addresses distinction, returned provenance, and required credentials. It stops short of describing result shape or rate limits, so a 4 rather than 5.

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 licence caveats are front-loaded in the first sentences, with auth/onboarding details trailing. Mostly earns its place, though the 'TerraMCP is a Wrench AI service' line and the odd 'hydrological units normalised to SI' clause add noise for this tool.

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 does describe what comes back (source data and provenance) and enumerates the credential prerequisites, which is what an agent needs before calling. The copy-pasted hydrological-unit note is irrelevant here but not harmful.

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 both parameters (query, limit) are already fully documented with bounds in the schema. The description's only added hint is the names-not-addresses caveat for the query, which is the baseline-3 situation.

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 (Search) and resource (OS Open Names in Great Britain), and clarifies the scope by noting these are names, not full postal addresses. It is distinguishable from the sibling hydrology/flood/station tools, though it never explicitly names an alternative.

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?

The description gives authentication context (vaulted OS Data Hub key, TerraMCP Bearer key) but no guidance on when to use this tool versus alternatives, nor any exclusion conditions. Usage must be inferred from the resource name alone.

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