list_users

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

Since there are no annotations, the description carries the full burden. It discloses the underlying mechanism (queries metrics API, groups traces by userId) and a default behavior (last 30 days). However, it does not explain ranking order, exclusion of zero-trace users, or pagination limits, leaving some behavioral ambiguity.

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?

The description is three sentences with the primary purpose front-loaded. Every sentence adds meaning: the first defines the tool, the second explains the implementation context, and the third gives a usage default. No redundant content.

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?

The tool has an output schema, so return values are covered. Yet the description omits details about parameter handling (top_n, project) and does not note whether the result is capped or sorted. It provides a workaround and alternative, but lacks some behavioral context necessary for full 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?

Schema description coverage is 0%, so the description must compensate. It only clarifies the timestamp parameters with the default 30-day window, but does not explain top_n (beyond 'top users') or the project parameter semantics, leaving two of four parameters under-specified.

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 a specific action ('List users') and resource ('users in the project') with a concrete output scope ('per-user trace counts', 'top users by trace count'). It also distinguishes the tool from alternatives by explaining that Langfuse lacks a dedicated /users endpoint and that this queries the metrics API.

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 description gives an explicit alternative for a scenario: 'Use fetch_traces(user_id=...) for a specific user's traces.' It also clarifies the default time range when timestamps are omitted. However, it does not list exclusions or when not to use this tool compared to other similar siblings like get_user_sessions.

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