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

Beyond the readOnlyHint annotation, the description discloses the exact return format, explains that 'project' is null for account-wide add-ons, and notes the permission requirement (billing scope). This provides substantial behavioral context not available from annotations alone.

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 only two sentences, front-loads the core purpose, and includes minimal yet essential details about the return structure and constraints. Every phrase contributes value without redundancy.

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?

With no parameters and no output schema, the description fully covers the return values, project semantics, and authentication requirements. It is complete for the tool's simplicity and leaves no obvious gaps.

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, so the rubric sets a baseline of 4. Since no parameters exist, the description does not need to add parameter-level meaning; it appropriately focuses on output and usage details.

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 explicitly says 'List the project owner`s currently-active add-ons', giving a specific verb and resource. It also clarifies the 'project' field meaning, distinguishing it from list_addons by focusing on active add-ons and ownership scope.

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 clearly states when the tool is usable: 'Owner-only' and 'requires a token minted with the billing scope'. However, it does not explicitly mention alternatives (e.g., list_addons) or when not to use it, so it lacks explicit exclusions.

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