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

The description goes well beyond the readOnlyHint and destructiveHint annotations. It details the semantics of 'readable: false' (events missing from get_availability, deliberately listed), 'writable: true' (create_event implications), 'notice' (user-changeable items, pass on), and 'sync_health' (does not affect availability reads). This is rich behavioral context that helps the agent interpret result fields correctly.

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 main purpose, then systematically explains each returned field in its own paragraph. Every sentence adds operational value, and the use of inline code formatting makes field names easy to scan. Despite being longer than average, it is not verbose.

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 that this is a simple list tool with no parameters and an output schema, the description fully covers the meaningful context: what the output fields mean, how they affect other tools, and how the agent should handle notice and sync_health. No significant gaps remain.

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 the input schema is empty, so schema coverage is effectively 100%. With no parameters to document, the baseline of 4 is appropriate; the description correctly focuses on output semantics rather than parameter syntax.

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 opens with 'Lists the calendars shared with this access, each with the detail level the user allowed,' which is a specific verb+resource statement. It clearly distinguishes the tool from siblings like get_availability and create_event by focusing on calendar metadata rather than events or mutations.

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 strong contextual guidance by explaining how readable/writable flags influence other tools (e.g., events missing from get_availability, create_event requiring calendar_id). However, it does not explicitly state when not to use this tool or name alternative tools, so it stops short of full exclusion guidance.

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