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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety is covered. The description adds meaningful context beyond that: it is free, it calls no upstream API, and it deliberately omits private values and upstream implementation details, which tells the agent what it will and will not learn.

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?

Three tight sentences front-loaded with the core action, then the payload contents, then the limits and cost. The enumerated field list is dense but each item earns its place; only the 'Never shows private values' clause slightly competes with the trailing 'Free; calls no API' for the closing emphasis.

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?

An output schema exists, so return structure need not be explained, yet the description still summarizes the payload's shape usefully. For a single-parameter, read-only tool, the only gap is the lack of an explicit statement about what happens when the vendor is unknown or has no published routes.

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% and the single parameter's description already says it is the vendor username from apiclay_search_apis. The tool description reinforces the 'one vendor' scoping, adding modest but real value on what the parameter selects; the pattern and format details remain the schema's job.

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 ('Show one vendor's API') and enumerates exactly what is returned: routes, tables, methods, paths, field types, delivery hints, pricing, and a ready-to-use call example. This clearly distinguishes it from apiclay_call_api (executes) and apiclay_search_apis (discovers vendors).

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 context is implied rather than stated: the description notes the output includes a ready-to-use apiclay_call_api argument example, which hints this is the step before calling. However, it never explicitly says 'use this before apiclay_call_api' or 'use apiclay_search_apis to find the vendor argument', leaving routing to inference.

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