Extract exact substrings from documents using bounded regex patterns. Selects verbatim source text without generating new values.
Find bounded regex candidates in a worker, then select a verbatim source substring. Never generates extracted values.
| Name | Required | Description | Default |
|---|---|---|---|
| fields | Yes | ||
| document | Yes | ||
| auto_accept | No | ||
| minimum_margin | No |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover safety (readOnlyHint, destructiveHint), so the description's job is to add behavioral context. It adds the important constraint 'Never generates extracted values,' clarifying that it only returns verbatim matches. This adds value beyond the annotations, though it doesn't cover all edge cases like no-match behavior.
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 extremely concise at two sentences, with the primary action front-loaded. Every word serves a purpose, and there is no redundant fluff. It efficiently conveys the core behavior in minimal space.
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's complexity (4 parameters, no output schema, no parameter descriptions), the description is far from complete. It does not explain what the tool returns, how parameters are used, or what 'bounded' means in this context. An agent would have many open questions when attempting to invoke 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 by explaining parameters. It fails to do so—no mention of 'document', 'fields', 'auto_accept', or 'minimum_margin'. The mention of 'regex' hints at the pattern field, but this is insufficient for an agent to understand how to fill the inputs correctly.
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 clearly states the tool's function: it finds bounded regex candidates and selects verbatim substrings. It uses specific verbs and a clear resource, distinguishing it from generic operations. However, it does not explicitly differentiate from sibling tools, so a perfect score is not warranted.
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 implies a use case for extraction from documents via regex, but it provides no explicit guidance on when to use this tool versus the many sibling tools. There are no when-not conditions or named alternatives, leaving usage partly inferred.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.