API Capabilities Inventory

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

Annotations provide readOnlyHint=true. Description adds details beyond this: 'live inventory', 'deterministic', 'no LLM cost'. These behavioral traits are valuable and do not contradict annotations.

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 with no wasted words. Front-loaded with the core purpose, followed by return structure and a key behavioral note (deterministic, no cost). Every sentence earns its place.

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 meta tool with no parameters and an output schema (as indicated by context), the description provides sufficient information about input, output, and usage context. No gaps remain for an agent to safely and effectively use this tool.

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?

Input schema has zero parameters, so schema coverage is 100%. The description adds value by detailing what the output includes (tool count, endpoint list, MCP-exposed tools, usage notes), which is more than just stating 'no parameters required'.

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 verb 'Return' and the resource 'live inventory of all active endpoints and MCP tools'. It distinguishes itself from sibling tools (like accessibility_check, colour_card, etc.) by being a metatool for discovery, not a domain-specific operation.

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?

Explicitly states 'Use this first to discover what the API can do before making calls', providing clear guidance on when to invoke. Mentions 'Deterministic -- no LLM cost', implying it's safe and cheap. No exclusions or alternatives given, but the context is clear.

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