list_roles

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

With no annotations, the description carries the behavioral transparency burden. It discloses that the output depends on project_id, changing from predefined to custom roles. It also states the return type. However, it doesn't mention potential errors, permissions, or pagination.

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 structured in a docstring with Args and Returns sections, containing only essential information. The Returns line is concise but adds marginal value, keeping the description efficient.

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 list tool with one optional parameter, the description covers the parameter behavior and return type. It lacks details on pagination or large result sets, but the simplicity of the tool makes this acceptable.

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 schema provides only the parameter name and type (null/string). The description adds meaning by explaining project_id selects custom roles, and its absence yields predefined roles. This fully compensates for the 0% schema coverage.

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 lists IAM roles, specifying predefined or custom variants. It uses a specific verb and resource, distinguishing it from sibling tools like get_role_permissions which focus on permissions.

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 explains when to provide project_id (for custom roles) and the default behavior (predefined roles), but it does not compare against alternative tools or state explicit exclusions. This provides context but lacks when-not guidance.

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