invariance_doctor

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

Annotations already establish readOnlyHint=true, and the description adds specific behavioral context: it checks API key auth, API reachability, and reports name/version, and it mirrors the CLI's JSON output. This gives the agent a clear model of what the call inspects without overpromising side effects.

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 tight sentences front-load the core purpose, then specify the CLI mirror and return shape. Every clause adds information, with no repetition or filler.

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 simple, zero-parameter, read-only diagnostic tool, the description is complete: it states the checks performed, notes the CLI equivalence, and documents the return shape. No output schema exists, so including the return structure is especially valuable and sufficient.

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?

With zero parameters and an empty input schema, there is no parameter information to document. The baseline for a no-parameter tool is 4, and the description sufficiently explains what the invocation does.

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 a specific verb and resource ('Run a health check on this MCP server') and enumerates exactly what it verifies: API key auth, API reachability, and server name/version. This clearly distinguishes it from the large set of sibling tools, none of which offer a server-wide diagnostic.

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 intended use case is implied by the description: call this when you need to verify server auth, connectivity, or identity. However, it does not explicitly state when to use it versus alternatives, provide exclusions, or name a fallback tool. The guidance is adequate but left to inference.

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