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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds context about the data source (British Geological Survey), licensing (Open Government Licence), and the fact that no auth is required. It also discloses the return fields. It does not mention pagination or rate limits, but the annotations cover the key behavioral traits, so the description adds value without contradicting annotations.

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 two sentences, front-loaded with the core purpose and scope, followed by return fields and data source/licensing. Every sentence earns its place. It is concise and well-structured, with no redundant information.

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?

The tool has an output schema, so return values are already documented. The description covers the data source, licensing, auth requirements, and the search scope. It does not explicitly mention the option to omit lat/lng for full coverage, but that is in the schema. For a read-only search tool with rich annotations and a full output schema, the description is nearly complete. A small gap is the lack of explicit mention of the full-coverage mode, but this is minor.

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 schema already documents all four parameters (lat, lng, limit, radius_km) with descriptions. The tool description adds context about the data being searched but does not add meaning beyond the schema for the parameters themselves. The schema descriptions are already detailed (e.g., 'must be supplied together with lng', 'default 20, max 100'), so the description's contribution is minimal. Baseline 3 is appropriate.

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 states a specific verb ('Search'), a specific resource ('Single Onshore Borehole Index (SOBI)'), and the scope ('near a point'). It also lists the return fields (reference number, site name, grid reference, depth, scan URL), which distinguishes it from sibling tools like bgs-ogcapi.geology.bedrock and bgs-ogcapi.hazards.earthquake_search. The title 'BGS Borehole Index Search' is reinforced but the description adds substantial detail beyond the title.

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 clearly states the tool searches borehole records near a point, which implies the use case of finding borehole data by location. It mentions 'no auth required' and the data source, which helps an agent understand prerequisites. However, it does not explicitly state when to use this tool versus alternatives like bgs-ogcapi.geology.bedrock or bgs-ogcapi.hazards.earthquake_search, nor does it mention the option to omit lat/lng for full Great Britain coverage (which is in the schema but not the description).

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