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

Annotations already declare readOnlyHint=false, destructiveHint=true, idempotentHint=false, and openWorldHint=true, so the safety profile is covered. The description adds the 'event must exist in the target account' precondition and the endpoint path, but does not explain the required confirm flag, partial-update semantics, or reversibility beyond what annotations state.

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 sentences, front-loaded with the action and endpoint, followed by the supported field set and limitations. No filler or repetition of the title.

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 19-parameter mutation with no output schema and a mandatory confirm flag, the description covers the main field groups and one precondition but leaves notable gaps: the confirm requirement, credential/account selection, and custom_fields format are undocumented in the description and only partially in the schema.

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 only 32% across 19 parameters, so the description must compensate. It lists the primary mutable fields (task/project linkage, start/end, notes, user, custom fields), giving real meaning for those, though it omits semantics for is_billed, event_type, include_custom_fields, and the credential/account parameters.

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 (update an existing time event), names the API endpoint, and enumerates the mutable fields (task/project linkage, start/end, notes, user, custom fields). This clearly separates it from create_event, delete_event, and update_events_batch.

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 'Limitations' clause gives a precondition (event must exist in the target account) and flags it as a write operation, which implies when it applies. However, it never routes the agent between this and alternatives like update_events_batch, restore_event, or stop_task, 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.