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

The readOnlyHint already establishes that this is a safe read operation. The description adds useful context beyond the annotation by naming the API endpoint, explaining that accountId comes from configured credentials, and stating the return type is a JSON array.

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 compact and front-loaded, starting with what the tool lists and its primary use case. The endpoint and return information follow without unnecessary detail.

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 tool with annotation coverage, the description is complete enough to call correctly. It explains the purpose, credential-derived accountId, endpoint, and that the result is a JSON array.

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 input parameters, so the schema baseline is 4. The description adds a relevant clarification that accountId is taken from configured credentials rather than supplied as a parameter.

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 uses a specific verb and resource: 'List the accounts/calendars available to your account.' It also states the concrete purpose, finding the calendarId for a team member, which distinguishes it from sibling tools such as list_profiles or list_team_members.

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?

It gives a clear usage context: the tool is 'used to find the calendarId for a team member.' However, it does not explicitly state when not to use it or name an alternative tool for obtaining that information.

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