regex-tester

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

With no annotations provided, the description carries the full burden of disclosure. It explicitly states 'Zero external API calls — instant, deterministic,' which is valuable behavioral context. It also implies safety and no side effects, though it could mention failure scenarios like invalid regex or overflow. Still, it goes beyond minimal.

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 sentences: first lists core actions, second emphasizes safety/performance, third suggests use cases. It is front-loaded, efficient, and every sentence serves a purpose with no 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?

The tool has no output schema, so the description must explain return values. While it mentions 'finds all matches (with capture groups), replaces text, and explains what the pattern matches,' it does not detail the output structure (e.g., whether matches are returned as an array, what fields like match, groups, explanation are present). For a regex tool, this omission hinders reliable invocation by an AI agent.

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?

The input schema describes all 4 parameters with detailed descriptions (e.g., pattern format, flags, input max length, replace_with usage). The description adds negligible extra meaning—it repeats 'replaces text' but doesn't clarify replacement semantics (e.g., $1 vs $&). With 100% schema coverage, 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 uses specific verbs ('validates', 'finds', 'replaces', 'explains') and clearly identifies the resource (regex patterns and text). It lists distinct operations, making the tool's purpose unmistakable and differentiating it from sibling tools that focus on other domains.

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 provides use cases: 'generating or debugging regex patterns mid-task, validating extracted data, or transforming text with precision.' However, it does not offer guidance on when not to use this tool or suggest alternatives (e.g., json-extract for JSON-specific extraction). The implied usage is clear but lacks exclusions.

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