calendar_list_instances

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

The description adds behavioral context beyond the readOnlyHint annotation by mentioning the requirement of a 'verified seriesMaster' and a 'bounded window.' It also alerts users not to derive IDs from dates, a valuable operational caveat. The read-only nature is already covered by annotations.

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 short sentences, directly states the main purpose first, and includes a clear usage directive. It is concise and well-structured without unnecessary verbosity.

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?

The description adequately explains what the tool does and how to use the returned data, referencing key fields. It does not mention pagination, error cases, or the exact response list format, but for a read-only instance lookup, the provided information is sufficient for typical usage.

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 description clarifies start and end as defining a 'bounded window' and seriesMasterId as needing a 'verified seriesMaster.' It also references 'originalStart' in the response, which helps understand the return shape. However, accountId is not explained beyond its name, and calendarId's description in the schema is not reinforced.

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 function with the verb 'Get' and specifies the resource: 'exact occurrence/exception IDs from a verified seriesMaster in a bounded window.' It also distinguishes this from general event listing by focusing on recurring series instances and explicitly mentions use for occurrence actions.

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 provides practical guidance on how to use the results ('Use returned ID, master and originalStart for occurrence actions') and warns against a common mistake ('never derive IDs from dates'). However, it does not explicitly compare to sibling tools like calendar_list_events, leaving the choice of this tool vs. alternatives somewhat implicit.

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