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

Annotations only declare it is a non-read-only, non-destructive, closed-world mutation. The description adds genuinely non-obvious behavior: replace-not-patch semantics for both fields, and a cross-resource side effect ("Any linked calendar event is reconciled to match") that no annotation conveys. It does not cover reversibility or failure modes, so not a 5.

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 short sentences, front-loaded with the operation and followed by the two behavioral facts an agent would otherwise get wrong. Nothing redundant or padded.

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 3-parameter mutation with no output schema, the description covers purpose, replace semantics, and the calendar-event side effect — enough to call it correctly. It does not describe the returned task representation or whether the calendar reconciliation can fail, a minor remaining 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 coverage is 100%, so the baseline is 3. The description earns above baseline by explaining why title is required even when only the date changes, which is a semantic the schema alone cannot convey; the omit-to-clear behavior for due_at is left entirely 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 (change) and resource (task) plus the exact editable fields (title and/or due date), which cleanly separates it from siblings like set_task_status, delete_task, or create_task. It never names an alternative sibling explicitly, so it stops short of a 5.

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?

"Both are replaced, so send the title even when only the date is changing" gives concrete calling guidance for the common edge case. It does not state when to prefer this over set_task_status or how to handle status changes alongside title edits, so no explicit exclusions.

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