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

Annotations already declare destructiveHint=true and readOnlyHint=false, but the description adds real behavioral context beyond them: the conflict failure on settled decisions, the possible `needs_confirmation` envelope, and the null-clears semantics for owner. It does not detail permissions or what a partial update leaves untouched.

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 dense sentences, fully front-loaded: core operation first, then the guardrail, then the failure/confirmation behavior. No filler.

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 13-parameter destructive mutation with no output schema, the description covers the main edit semantics, the state gate, and the confirmation path, which is what an agent most needs. It stops short of explaining the time-zone/start-end time interaction and the note/tags fields, leaving a small 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 only 46%, so the description must compensate and does for several fields: it maps dueOn to move, title to rename, ownerUserId null to clearing, url to attaching a link, and lists the status enum. However it omits the timing trio (startTime/endTime/timeZone), note, and tags, so meaningful parameters remain undocumented in the description.

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 ('Edits one plan item') and enumerates the exact edit operations (move via dueOn, rename, re-own, attach link, set status). This clearly separates it from the ledger_plan_add/delete/list siblings without needing to open their schemas.

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 when ('while its decision is open'), a when-not with the failure mode ('Fails with conflict once the decision is settled'), and a strong operational rule ('Mark done only when the user says it shipped; a link alone doesn't mean done'). Little is left to inference.

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