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

Beyond the annotations (destructive, non-idempotent, open-world), the description discloses the confirmation/owner-approval flow, that the schedule can be toggled on this tool, that a scheduled post remains editable until it goes out, and that email delivery is a side effect controllable via send_email. These are exactly the facts an agent needs before committing a destructive, hard-to-undo action.

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?

The first two sentences say nearly the same thing twice ("Publish a draft at a set time, on the web and by email" / "Schedules a draft to go live at the time you set, on the web and, unless send_email is false, by email"), and the confirmation sentence trails after the substantive constraints. Constraints are covered but the front-loading is undermined by that duplication.

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 mutation tool with annotations but no output schema, the description covers validation failures, approval behavior, post-scheduling editability, target-section routing, and email side effects — enough to call it correctly. Missing only what the call returns and how to verify the scheduled result.

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 all four parameters are already documented, including section_id's fallback chain and send_email's default. The description restates the section resolution order and the email opt-out but adds no new syntax or format detail; baseline 3 is appropriate.

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 opens with a specific verb and resource ("Publish a draft at a set time, on the web and by email") and the phrase "at the time you set" distinguishes it from immediate publishing (publish_post) and from cancel_scheduled_post. An agent can identify the operation without inspecting 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?

It states concrete preconditions — the time must carry a time zone and be in the future, and Substack's pre-publish check blocks missing titles or empty bodies — which tells the agent when the call will fail. It does not explicitly compare against the close alternatives publish_post or update_draft, so the routing guidance is implied rather than stated.

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