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

Annotations already declare readOnlyHint=true, so the safe-read profile is covered. The description adds the account scoping constraint and the v3 endpoint path, but says nothing about pagination behavior or result shape beyond what the schema's page_token/limit already imply.

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 compact sentences, front-loaded with the purpose and followed by the endpoint reference. The raw HTTP path is mildly redundant for an agent but is short and can aid debugging.

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 list tool with full schema coverage, an explicit readOnlyHint, and no output schema requiring explanation, the description covers scope, purpose, and sibling relevance adequately. Pagination mechanics are left entirely to the schema, which is the only real gap.

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%, so limit, grant_id, and page_token are all documented in the schema itself. The description only implies the account-scoping semantics of grant_id ('for the connected account') and adds no format or usage detail beyond the schema — baseline 3 applies.

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?

States a specific verb and resource ('List calendars') scoped to the connected account, and adds a useful cross-reference that each result carries a calendar_id used by the events tools. It does not explicitly contrast itself with siblings like nylas_list_events or nylas_get_calendar, but the purpose is unambiguous.

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 clause '(each has a calendar_id used by the events tools)' implicitly signals that this tool is a prerequisite for the events tools, which is helpful context. However, there is no explicit when-to-use/when-not-to-use guidance or named alternative (e.g., get_calendar for a single calendar), so usage is only implied.

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