Use recorded cassettes to test MCP servers offline. Run all checks against saved responses, enabling validation in CI without a live server.
Use this to test a server without running it. Replays a previously recorded cassette offline and runs all checks against the recorded responses. Useful in CI or when the live server is unavailable.
| Name | Required | Description | Default |
|---|---|---|---|
| cassette | Yes | Path to a cassette JSON file. |
Changes observed during successful MCP inspections.
v1.35.4v1.33.0v0.11.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description discloses that the tool runs offline and replays recorded responses, but does not specify side effects (e.g., no modifications) or output format. Since no annotations are provided, the description carries the full burden and could be more detailed.
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, front-loaded with purpose, and every sentence adds value. No unnecessary words.
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 description explains purpose, behavior, and use cases but does not mention the output format or return value, which is important since no output schema is provided. For a simple tool, it's adequate but incomplete.
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 coverage is 100% with a description for the 'cassette' parameter. The description adds no additional semantic value beyond the schema, so 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 clearly states the tool replays a recorded cassette to test a server offline, which is a specific verb-resource combination. It distinguishes from sibling tools like 'check_server' which likely test live servers.
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 explicitly mentions usefulness in CI or when the live server is unavailable, giving clear context for when to use. It lacks explicit when-not-to-use or alternative mentions, but the context is strong enough.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.