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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds a useful precondition (exact calendar ID, not a name) but does not add behavioral detail such as return format or not-found behavior. This is adequate given the strong annotation coverage.

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 short, front-loaded, and communicates the essential rule about exact IDs and display-name rejection. There is some redundancy between the first sentence and the 'Calendar ID:' elaboration, but it remains compact and scannable.

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 read-only get-by-ID tool, the description plus annotations cover the safety profile and the key prerequisite. The account_id nuance is fully handled in the schema. A brief statement of the return shape would be a minor enhancement, but nothing essential is missing for correct invocation.

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?

Schema description coverage is 100%, and both parameters are well-documented in the schema, including the exact-ID rule for calendar_id and detailed account disambiguation for account_id. The tool description mostly repeats the calendar_id guidance already present in the schema, adding no new parameter meaning.

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 states a specific verb and resource: 'Get one calendar by the exact ID'. It clearly distinguishes this from the sibling calendar_list_calendars and calendar_get_event tools by emphasizing that it fetches a single calendar using an exact ID.

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 gives clear context on how to obtain the required ID ('returned by calendar_list_calendars') and explicitly warns against passing a display name. It does not explicitly enumerate when to prefer this over alternatives, but the exact-ID prerequisite makes the intended usage clear.

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