list_calendars

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

With no annotations, the description carries the full burden. It states that it lists all available calendars and implies the output contains URLs, which is helpful. However, it does not disclose behavioral nuances like whether it filters by authenticated user, handles pagination, or makes any assumptions about 'available'. This is adequate but not exhaustive.

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?

Two sentences, each earning its place. The first states the action and scope, the second provides the practical purpose. No filler, front-loaded with the operation.

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 zero-parameter, read-only list operation with no output schema, the description is complete. It tells an agent what it will receive (calendar URLs) and why to use it, which is all that's necessary to call it correctly.

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?

There are zero parameters, matching the baseline of 4. The description doesn't need to add parameter details since none exist, and it correctly doesn't attempt to fabricate any.

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 names the verb 'List', the resource 'all available calendars', and the source 'from the CalDAV server', which is specific and unambiguous. It clearly differentiates from sibling tools like list_events and list_contacts by focusing on calendars, and the name itself aligns perfectly with the domain.

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 phrase 'Use this to get calendar URLs needed for other operations' provides an explicit use case, telling an agent why and when to invoke this tool. It does not explicitly name alternatives or provide exclusion criteria (e.g., 'when you already have calendar IDs'), but the context is clear enough for a simple list operation.

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