calendar_events_update

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

With no annotations, the description carries the full burden and does reasonably well: it flags SIDE-EFFECTFUL, discloses the merge-then-revalidate behavior, and names a concrete failure case (`ends_at` below `starts_at` throws), plus the return shape. It omits permission/auth requirements and reversibility, which are relevant for a mutation.

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?

Three tight sentences, front-loaded with the SIDE-EFFECTFUL warning, then the operation, then the validation/return contract. No filler.

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?

Given 9 params already fully documented by the schema, no output schema, and no annotations, the description covers the essentials: what it mutates, the validation failure mode, and the return shape. Only auth/permission context is missing, which is minor against otherwise complete coverage.

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 the baseline is 3, but the description adds meaning beyond the schema by explaining that fields like entity/title can be patched and by describing the interaction constraint between `ends_at` and `starts_at`. It still leaves most parameter syntax (ISO formats, freeform fields) to the schema.

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 (patch) and resource (an existing event), and enumerates the kinds of changes allowed (move, retitle, re-home to another entity). The word 'existing' cleanly separates it from calendar_events_add and calendar_events_delete.

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?

Usage is implied by 'Patch an existing event', which signals this is for modifying, not creating. However, no explicit when-to-use/when-not guidance or named alternatives (e.g. add/delete) are given, and no prerequisites are stated.

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