Get usage per project

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

Annotations already declare the tool read-only and idempotent. The description adds valuable context: it returns per-project data, can be filtered by a single project, and is restricted to organization keys. This goes beyond what annotations state, though it does not explain default behavior when no projectId is given.

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 concise and well-structured: it opens with the core output and purpose, then clarifies optional filtering and authorization constraints. Every sentence earns its place without repetition or fluff.

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 simple tool with two optional parameters and no output schema, the description covers purpose, optional filter behavior, and key restrictions. It does not explicitly state what happens without projectId (likely all projects), but this is reasonably inferable from 'per project' and the optional parameter.

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 input schema fully describes both parameters (month with pattern and default, projectId with format). The description enriches meaning by clarifying that projectId scopes the result to a single project ('that project only'), which is helpful and not redundant with the schema.

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 tool retrieves usage numbers, proxy traffic, and messages per project for a month, with a specific purpose (rebilling). It distinguishes from the sibling 'get_usage' by explicitly saying 'per project', making its scope clear.

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 provides concrete usage guidance: 'With projectId, that project only' tells when to filter, and 'Organization keys only' specifies authorization context. It does not explicitly name alternatives like 'get_usage' for overall usage, but the per-project focus inherently differentiates it.

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