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

The annotations declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with "opens nothing by itself", resolving the apparent tension between the name "create_post" and the read-only hint. It also adds context about Substack's limited official API, though the remark "checked 11 Oct 2026" is an unverifiable/odd date and no auth or Cloud Browser session prerequisites are stated.

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 core fact — that this returns instructions rather than performing the action — is buried mid-sentence behind a promotional opener ("from ChatGPT, Claude or any AI agent"). The semicolon-chained run-on and the trailing API aside add length without adding decision-relevant 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 parameters and no output schema, the description must carry the return-value burden, and it only loosely characterizes the output as step-by-step screens/buttons/fields without stating the format. It never names a prerequisite such as an open Cloud Browser session or authenticated Substack account, which an agent would need before following its instructions.

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?

The schema takes zero parameters (additionalProperties: false), so there is nothing for the description to disambiguate. Baseline 4 applies; the description correctly implies no input is required.

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 does say what the tool returns ("step by step (screens, buttons, fields)") and clarifies it "opens nothing by itself", which is meaningful. But the leading sentence "Create post in the user's own Substack account" reads as if it performs the creation, and it never distinguishes this tool from the sibling `create_post`, `create_draft`, or `publish_post`, so an agent cannot tell which of these actually writes the post.

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 gives a clear follow-on workflow ("then do it with the cotlet_browser_* tools in the user's Substack Cloud Browser"), which is real sequencing guidance. It offers no when-not guidance and does not say why an agent would pick this guide tool over the sibling `create_post` that appears to do the same job directly.

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