describe_engineShows an engine's input schema, including required fields, units, alternative shapes, and a worked example so agents can submit valid inputs and avoid rejected requests.
Shows one engine's input schema: required fields, units, alternative shapes, and a worked example. Engines reject bad input rather than guessing.
| Name | Required | Description | Default |
|---|---|---|---|
| engine | Yes | Engine id. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this a read-only, idempotent, non-destructive, closed-world call, so the safety profile is covered. The description adds a genuinely useful behavioral trait not in the annotations: engines fail fast on invalid input rather than coercing or guessing, which tells the agent to treat the schema as strict.
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?
Two sentences, both load-bearing: the first front-loads what is returned, the second adds the fail-fast behavior. No filler, no restatement of the tool name or title.
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 one-parameter, read-only lookup with no output schema, the description covers purpose, return content, and the validation behavior. It is nearly complete, lacking only a pointer that engine ids come from list_engines.
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?
There is a single parameter ('engine') with 100% schema description coverage, so the schema already documents it as an engine id. The phrase 'one engine's input schema' confirms the parameter selects which schema is returned but adds no format or sourcing detail beyond the schema.
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 states a specific verb and resource — 'Shows one engine's input schema' — and enumerates what the output contains (required fields, units, alternative shapes, worked example). This clearly separates it from list_engines and run_engine, though it never names a sibling explicitly.
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 only implied: the note 'Engines reject bad input rather than guessing' hints that this should be consulted before calling run_engine with unfamiliar arguments, but no explicit when-to-use instruction or alternative is offered. An agent can infer the workflow but must do the inference itself.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.