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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it clarifies the data source (British Geological Survey), the licensing (Open Government Licence), that no auth is required, and what the returned fields are. It does not mention rate limits or pagination, but with annotations covering safety, the description adds meaningful context beyond them.

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 three concise sentences with zero filler. The primary purpose is front-loaded, followed by the key period distinction and then return/data/license details. Every sentence contributes distinct information without redundancy.

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?

Given that the schema is rich (full descriptions for all params), an output schema exists, and annotations cover safety, the description provides sufficient complementary context: it explains the two catalog periods, return fields, data origin, licensing, and auth. It does not elaborate on parameter interactions or sorting, but the schema already covers parameter intent. The description is adequate for an agent to correctly select and invoke the tool.

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 fully documents all 7 parameters, including the lat/lng pairing and the period enum. The description adds some explanation of the period values (modern vs historical) and notes the default, but this is also present in the schema's enum descriptions. The description does not significantly exceed the schema; it restates some details but does not compensate for missing coverage since there is none. 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 clearly states the tool searches UK earthquakes by specific filters (area, year, minimum magnitude) and lists return fields. It differentiates from similar tools like earthquake.events.search by explicitly scoping to the UK, and further narrows via the two catalog periods. The verb and resource are unambiguous.

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 clear context on scope (UK only) and explains the two period options, but does not explicitly name alternative tools or state when not to use this one. It implicitly tells users this is for UK earthquake data, but lacks a direct 'for other regions use X' statement. The period explanation provides some usage guidance, but not exhaustive.

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