Complete a to-do

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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false. The description adds genuine context beyond them: the exact success string, that re-completing a done item is a no-op, and the three-state approval flow with its return strings (allowed / "Waiting for approval in Sara" / off). The only shortfall is that the idempotent no-op restates the annotation rather than extending it.

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?

Front-loaded with the core action, then alternatives, then return value, then permission gating — a sensible ordering. The approval-gating sentence is long and packs three branches into one line, which costs a little readability but each clause carries distinct information.

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?

With no output schema, the description supplies the exact return string, plus the approval and disabled-state responses an agent must be able to recognize. Idempotency, error behavior, and permission prerequisites are all covered, so nothing needed to call it correctly is missing.

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 the single id parameter already documents its provenance and the unknown-id error, so the baseline of 3 applies. The description reinforces the id source but adds no syntax or format detail beyond 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 and resource ("Mark one of the owner's to-dos in Sara as done, by its id") and implicitly scopes it against delete_task and update_task by naming update_task as the reopen path. An agent can distinguish it from every sibling without opening a 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?

Explicitly says where ids come from (list_tasks or get_today) and names the alternative for the inverse operation (update_task with status "open"). It also states the precondition that the tool is only listed when the owner enables "Let other apps change things", which is real when-to-use guidance.

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