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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds real behavioral context beyond them: the fields each hit contains and a hard cap of 100 results, which is the kind of constraint an agent needs to plan pagination or narrow its query.

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?

Four short sentences, zero filler, with the core purpose front-loaded and the limit and the sibling exclusion trailing. Every sentence carries 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?

With no output schema, the description usefully enumerates the returned fields (statement, plain reading, fix, source URL) and the 100-hit cap, which is enough to call it correctly. It omits any hint about preferring get_rule for a single known rule, leaving a small gap for a four-tool family.

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 coverage is 100%, so the schema already documents bt, group, and query in detail (pattern, enum list, matching rules). The description only restates the three axes in prose and adds no syntax or interaction detail, so the 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 ('Find') plus the resource ('stored rules') and the three lookup axes (words, BT code, group). The closing clause 'Does not check an invoice' draws a hard boundary against the check_invoice sibling, so an agent can route without opening either schema.

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 when this is the right call (lookup of stored rules by text/code/group) and one explicit exclusion ('Does not check an invoice'). It stops short of routing to get_rule for single-rule retrieval or stating that all three filters are optional and combinable.

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