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

Adds substantial context beyond the annotations: nothing is sent until publish/schedule, the draft is visible only to the team, it returns post_id, and it requires the user's Cotlet API key with access to the app. This goes well past what destructiveHint=false/openWorldHint=true convey.

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 purpose and scoping, but the 'nothing is sent / sending is a separate step / reaches no one' idea is restated three times, so it is slightly repetitive rather than maximally tight.

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, it correctly states the return value (post_id), covers visibility, the send-is-separate workflow, and the auth prerequisite. An agent has everything needed to call it correctly.

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 title, subtitle, body_markdown and the audience enum are already documented. The description only adds 'from Markdown' about the body format; baseline 3 is appropriate when the schema does the heavy lifting.

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 — 'Creates a draft in your publication and returns its post_id' — and explicitly distinguishes itself from the publishing siblings (schedule_post, publish_post) and update_draft. An agent can tell this apart from the other Substack write tools 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?

Names the alternatives with their conditions: 'Sending is a separate step: schedule_post or publish_post' and 'update_draft or the Substack editor changes it.' It also signals no confirmation is needed ('runs without asking'), which clarifies when to just call it.

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