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

Annotations already declare readOnly, idempotent, open-world and non-destructive behavior, so the bar is lower. The description adds real context beyond them: the authoritative source (Historic England Register of Historic Battlefields), a coverage limitation (registered sites in England only), and a per-call cost of 1 credit.

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?

A single compact paragraph that front-loads the verb and resource, then layers source, scope and cost. Every sentence carries information, though the audience clause is the weakest and could be trimmed without loss.

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 two-parameter read-only lookup with no output schema, the description is nearly sufficient: it names the dataset, enumerates returned fields, states the geographic/registration scope limit and the credit cost. Only pagination behavior and how name matching works are unstated, which are minor gaps.

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 (name substring, limit 1-100 default 25) are already fully documented. The description's field list describes return values rather than adding syntax or semantics for the inputs, so it contributes nothing beyond the schema; 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 and resource ('List or search England's registered historic battlefields') and enumerates the returned fields (name, battle year, date registered, area, grid reference, link). It also carves out scope against the many heritage siblings by noting it covers only registered battlefield sites in England, not every recorded battle.

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?

Offers audience-level context ('for history fans, schools and walkers asking where a battle was fought'), which implies when the tool is useful. It never names an alternative (e.g. scheduled_monument_search, protected_wreck_search, historic_park_garden_search) or states when not to use it, so routing between the similar heritage tools 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.