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

Annotations already say this is a non-destructive, non-read-only write, so the bar is lower. The description nonetheless adds genuinely useful behavioral context by pre-empting the obvious fear: setting a plan date does not schedule or send anything, which is not derivable from destructiveHint=false. It stops short of saying what an existing planned date is replaced by or what the call returns.

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, both earning their place, with the action stated first and the disambiguation clause immediately after. No filler or repetition of the title.

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?

Three well-documented parameters, no output schema, and annotations covering the safety profile: the description is nearly sufficient as-is. The remaining gap is minor — no statement of whether the project parameter matters in multi-project accounts or what a success response looks like — but neither blocks correct invocation.

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 100%, and the schema itself already documents the day format, the today-to-90-days window, null-clearing, and the post_id/project sourcing. The description restates the editorial-date-only meaning of 'day' but adds no syntax or edge-case detail beyond the schema, so baseline 3 applies.

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?

The description names a specific verb pair (sets or clears) and a specific resource (the day a post is planned for), then bounds it: 'Only the editorial date: nothing is scheduled or sent.' That boundary separates it from publish/schedule-flavored siblings and from the calendar-reading tools in the sibling list, so an agent can pick it without opening the 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?

Usage is implied rather than stated: it tells you the operation clears when the value is null, but never names when to reach for this instead of siblings such as uptake_calendar, uptake_update_move, or uptake_write_post. There are no prerequisites or exclusions, so the agent must infer routing from the sibling names.

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