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

With no annotations, the description carries the full burden. It discloses the effect (member sees project and logs time) and mentions idempotency_key for retry safety. It also notes the organization is fixed by context. Lacks details on permissions or reversibility, but sufficient for a straightforward assignment.

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 essential information front-loaded: purpose first, then parameter guidance. No unnecessary words or repetition.

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?

Given no output schema or annotations, the description covers the main action, parameter selection, and idempotency. It does not describe return values or error handling, but for a simple assignment tool, this is adequate.

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?

Despite 100% schema coverage, the description adds significant value: it clarifies that email is preferred over org_user_id, directs to use find_billing_work for project_id, and explains idempotency_key behavior. This goes beyond the schema's descriptions.

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 assigns a member to a project, specifying the outcome ('so they can see it and log time against its tasks'). The verb 'assign' and resource 'member to project' are specific and distinguish it from siblings like assign_user_to_customer.

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 explicit guidance on when to use (to give project access and time logging ability), how to identify members (email preferred or org_user_id), and how to get the project_id (via find_billing_work, never ask user). It implies when not to use (e.g., if project_id unknown) but does not explicitly state exclusions.

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