Test a regex pattern against text and return every match with its position, helping validate patterns and inspect match results.
Test a regex pattern against text and return all matches with positions.
| Name | Required | Description | Default |
|---|---|---|---|
| text | Yes | Text to test against. | |
| flags | No | Regex flags (default: g). Options: g, i, m, s. | |
| pattern | Yes | Regular expression pattern. |
Changes observed during successful MCP inspections.
v0.1.11Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavior by stating the return shape ('all matches with positions'), but omits the regex engine/flavor, catastrophic-backtracking risk, and how the default 'g' flag affects results when unset.
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?
A single front-loaded sentence with no filler; the core action and the return value are both stated up front.
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 is the only source of return-value information, and 'all matches with positions' is a thin sketch. For a regex tool, the engine flavor and empty-match/no-match behavior are the details an agent most needs and they are absent.
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 100%: the schema already documents pattern, text, and flags (with the default 'g' and the valid flag options). The description adds nothing beyond that, 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 and resource ('Test a regex pattern against text') and even previews the return ('all matches with positions'). No sibling tool offers regex matching, so ambiguity is low, but the description does not explicitly differentiate from adjacent string-search tools like rabin_karp_search or kmp_search.
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?
Usage is implied by the name and description — an agent can infer this is the tool for regex evaluation. However, there is no statement of when to use it versus a literal-substring tool, and no note about invalid-pattern handling or error behavior.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.