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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses the complete set of returned fields and explicitly states the safety profile by saying both humans and agents can call it, implying no special restrictions or destructive side effects. It doesn't mention error cases or permission requirements, but for a read-only billing summary, this is adequate.

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 two sentences with no filler. The first sentence efficiently enumerates all returned data, and the second adds practical usage guidance. Every clause contributes value.

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?

Despite lacking an output schema and annotations, the description fully enumerates the return fields (plan, gated resource counts/caps, price, card, invoice date) and provides usage context. The sibling list includes related billing tools, so the tool's place is clear. This is a complete description for a simple zero-parameter getter.

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 is an empty object, confirming zero parameters. The description doesn't describe any parameters because none exist, so the baseline 4 applies for 0-param tools.

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 'Get' and a specific resource 'the caller's org billing summary', and enumerates the exact fields returned (plan, counts, caps, price, card, invoice date). This clearly distinguishes it from sibling billing tools like upgrade_plan and downgrade_plan.

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?

Explicitly states when to use it in relation to upgrade_plan: 'Use before upgrade_plan to check whether you're actually capped, and after to confirm the new plan landed.' Also notes that 'Both humans and agents can call this,' providing accessibility context. Though it doesn't exhaustively list all alternatives, it names the primary related tool.

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