list_calendars

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

With no annotations provided, the description carries the full burden. It states the key behavioral nuance that only calendars holding events are returned, and reminder lists are excluded. It does not explicitly state it is read-only, but that is implicitly clear from the verb 'list.' A slightly stronger disclosure of side-effect-free behavior would warrant a 5.

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, front-loaded with the primary purpose, and every clause adds value. No redundant or filler wording.

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 having no output schema, the description explains the return values (IDs, names, colors) and the filtering behavior. It is complete for a simple list operation with no parameters.

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 schema fully covers this aspect. The description adds no parameter-specific information, but none is needed. A baseline of 4 is given per instructions for zero-parameter 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 clearly states the tool's purpose: 'List the user's calendars.' It specifies the resource (calendars), the action (list), and the returned data (IDs, names, colors). It also distinguishes itself from sibling event-management tools by noting its role in finding a calendar to add events to.

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 explicitly instructs when to use it: 'Use this to find which calendar to add events to.' It also provides an exclusion—'Only calendars that hold events are listed; reminder lists are not part of this server's surface'—which helps avoid misuse.

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