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

Annotations already declare read-only, idempotent, non-destructive behavior. The description goes well beyond them by disclosing the exact line types returned (BILL, CREDIT, NOTE), state-dependent behavior for unauthenticated/unclaimed callers, and the remedy path.

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 front-loaded with the core purpose, then structured into output-line details and follow-up guidance. Each sentence adds distinct operational information with no filler.

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 self-sufficient: it covers the report contents, conditional return lines, entitlement states, and next steps. Nothing an agent needs to call it correctly appears to be missing.

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 and 100% schema coverage, so the baseline is 4. The description adds value by explaining what the report contains, compensating for the absence of any parameter documentation.

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 uses a specific verb ('Report') and a clear resource (the agent's resolved identity, funded account, plan, and entitlements). It differentiates from siblings like get_plans by focusing on the caller's resolved identity and current grant, not on available plans.

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?

Provides clear context and explicit conditional branching ('If unauthenticated, call register_agent next') and describes when a NOTE is returned. It does not explicitly compare against sibling alternatives like get_plans, but the described next steps are actionable.

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