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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool returns matches and groups, but does not disclose regex flavor (e.g., PCRE, ECMAScript), flags support, error behavior for invalid patterns, or whether it returns all matches or just the first. This is a significant gap for a testing tool.

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 a single concise sentence that front-loads the core action and return value. It is efficient, though it omits important behavioral details that would make it more useful.

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 the tool has an output schema, the return structure is covered, but the description lacks essential context: regex flavor, flags, error handling, and match semantics. For a tool with no annotations and 0% schema coverage, this is incomplete. An agent would likely need to inspect the output schema or experiment to use it correctly.

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 0%, so the description must compensate. It names 'pattern' and 'text' implicitly via 'Test a regex', but does not explain the semantics of each parameter, such as what 'text' represents or how 'pattern' is interpreted. The description adds minimal meaning beyond the schema's field names.

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 'Test a regex; return matches + groups.' clearly states the verb (test) and resource (regex), and the return value (matches + groups). It distinguishes itself from the sibling tools, which are mostly encoding/decoding/formatting utilities, though it doesn't explicitly name 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?

No guidance is given on when to use this tool versus alternatives. The sibling list contains no other regex tool, so the intended use is implied, but there is no explicit context about when to choose this over, say, string_metrics or case_convert. The description does not state any exclusions or prerequisites.

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