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

Goes well beyond the annotations (readOnly=false, destructive=false) by disclosing the non-obvious side effect that completing removes the task's calendar event, plus the rationale (the calendar shows open work only) and that the effect is reversible via reopen. That side-effect and reversibility information is exactly what an agent needs before mutating 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, zero waste, front-loaded with the action and then the side effect and its rationale. Every clause carries information the agent could not get from the schema.

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 two-required-parameter mutation tool with no output schema and full schema coverage, the description covers action, effect, reversibility, and rationale. It does not say what is returned or how failures (e.g. unknown task_id) behave, which is 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% and already documents both parameters, but the description adds meaning by tying each value to a consequence: completing (done=true) deletes the calendar event, reopening (done=false) restores it. That goes beyond 'true to complete, false to reopen'.

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 ('Mark a task done or put it back to open'), and the state-toggle framing makes it unambiguously distinct from update_task (field edits) and delete_task (removal) among its siblings.

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?

Covers both usage directions explicitly — completing versus reopening — with the implication that this is the tool for status changes. It stops short of naming update_task or delete_task as the alternatives, so there are no explicit exclusions.

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