list_capabilities

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

No annotations are provided, so the description carries the full burden. It reveals one behavioral aspect: the result depends on the configured API key mode. However, it does not disclose read-only nature, permissions, or output structure. Adequate but minimal.

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?

Single sentence that is front-loaded with the action and resource. Every word is informative, no redundancy. Ideal conciseness for a simple listing tool.

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 zero-parameter tool with no output schema, the description is mostly complete. It tells what it does and the dependency on API key mode. However, it could briefly mention that the output is a list of capability strings to aid agent understanding.

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?

The tool has zero parameters with 100% schema coverage (trivially). Per rubric, baseline is 4. The description does not need to add parameter information, and it does not.

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?

Description uses the verb 'Lists' and specifies the resource 'capabilities currently available on this MCP server'. It clearly distinguishes itself from sibling tools like list_mcc_codes and search_merchants, which cover different domains.

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?

Description implies usage to discover available capabilities based on API key mode, but lacks explicit when-to-use or when-not-to-use guidance compared to alternatives. No sibling tool serves the same purpose, so no exclusion needed.

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