List Users

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

No annotations are provided, so the description carries the full disclosure burden. 'All registered' hints at an unfiltered read but says nothing about authentication requirements, rate limits, result ordering, or pagination behavior for a potentially large list. Only the return shape is covered, and that is supplied by the output schema rather than the description.

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?

A single short sentence with the scope constraint ('all registered') front-loaded and zero filler. Nothing in the sentence could be removed without losing information.

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 read tool with an output schema that already documents the returned username list, the description covers the essentials. The only gap is the absence of any operational context (auth, expected volume), which for a simple enumeration tool is minor.

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 takes zero parameters, so there is no parameter semantics for the description to explain; the baseline for a parameterless tool applies. No credit above baseline is earned since there is nothing extra to clarify.

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 (List) and resource (registered Foursquare usernames), and even narrows the payload to usernames rather than full user objects, which is more precise than the title. It does not, however, distinguish itself from siblings like search_all_users_checkins or get_user_details, so it stops short of a 5.

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?

There is no when-to-use guidance, no statement of exclusions ('no filtering by check-in or venue'), and no pointer to the sibling that handles a related lookup. The agent must infer that this is the unfiltered enumeration tool.

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