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

Annotations already carry the safety profile (readOnlyHint=false, destructiveHint=false), and the description's 'Correct or enrich' wording is consistent with a non-destructive mutation. The description adds the scope of what can be changed but stays silent on whether omitted fields are preserved, whether the event must pre-exist, and what the response contains. No contradiction with annotations; the added behavioral value beyond annotations is moderate.

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 tight sentences: the first front-loads the verb and resource, then enumerates editable fields; the second delivers the routing rule. Every clause earns its place, with no filler and no repetition of details already encoded in the schema or annotations.

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 9-parameter mutation with no output schema, the description covers purpose, selection, and editable scope well, and the schema's ends_on annotation adds the empty-string-clears behavior. But the description itself omits update semantics (are unsupplied fields preserved or cleared?), the requirement that the event already exist, and any indication of the return value or error behavior, leaving the invocation contract incomplete.

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 22%, so the description must compensate — and it partially does by mapping plain-language fields ('title, description, category, dates, impact note or link') onto most parameters. However, it never mentions the sole required parameter event_id (the update target) and gives no hint about task_id's role, leaving two schema parameters — one of them essential — without added 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?

States a specific verb+resource pair ('Correct or enrich a project timeline event') and enumerates exactly which fields are in scope ('title, description, category, dates, impact note or link'). The closing clause frames it as an edit rather than a duplicate log entry, which distinguishes it from the sibling log_project_event without needing to open either schema.

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?

Gives an explicit selection condition: 'Use this instead of logging a duplicate event when the facts change.' This tells the agent when to prefer an update over creating a new timeline entry. It falls just short of a 5 because the alternative is described behaviorally ('logging a duplicate event') rather than naming the sibling tool log_project_event explicitly.

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