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

No annotations are provided, so the description carries the full burden. It does disclose the return shape (match status, capture groups, span), which is genuinely useful given there is no output schema, but it says nothing about error behavior on an invalid pattern, flag-handling, or that the operation is side-effect free.

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?

One compact sentence, front-loaded with the action and trailing the return contract. No wasted words, though it is terse enough that the missing flag and alternatives were squeezed out.

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 small pure-function tool the description covers the gist, but with a nested schema at 0% description coverage, no annotations, and no output schema, the unmentioned ignore_case field and absent invalid-pattern behavior leave gaps an agent would need to probe.

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% and the single parameter is a nested object, so the description must compensate. It conveys 'pattern' and 'text' conceptually but completely omits the ignore_case flag, leaving one of three nested fields undocumented anywhere.

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?

Clear specific verb+resource: tests a regex against text and states the outputs (match status, capture groups, span). It does not, however, distinguish itself from the sibling regex_replace, which is the nearest neighbor an agent could confuse it with.

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 explicit when-to-use guidance or exclusions. The verb 'test' implies non-mutating evaluation, but the description never contrasts with regex_replace or states when testing (rather than matching/replacing in a pipeline) is the right call.

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