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

Annotations declare readOnlyHint=true, and the description reinforces that with the explicit statement that it "opens nothing by itself" — a genuine clarification of the boundary. It also discloses the return shape (step-by-step screens, buttons, fields) and the required follow-up tool family. It stops short of noting auth requirements or limits on freshness of the guidance.

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 two sentences are front-loaded and efficient, but the trailing fragment "Substack's official API: Substack has only a limited API (checked 11 Oct 2026)" is a dangling label-value splice that reads as an orphaned note and adds little for a tool that returns UI instructions. The parenthetical date also ages the text without stating why it matters.

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, no output schema, and annotations already covering the safety profile, the description supplies what an agent actually needs: that it returns procedural guidance and that execution happens via cotlet_browser_*. The remaining gap is the missing tie-break against the sibling reply_to_note, which would matter for correct tool selection.

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?

There are zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. The description correctly implies a call with no arguments. No parameter meaning is added or needed.

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 states a concrete outcome: it "Returns how to do it in Substack step by step (screens, buttons, fields) and opens nothing by itself." That correctly recharacterizes what the misleadingly action-flavored name implies, so an agent learns this is a guide, not a write. It does not, however, distinguish itself from the near-identical sibling reply_to_note, which is the main ambiguity risk.

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 usable sequence: call this first, then "do it with the cotlet_browser_* tools in the user's Substack Cloud Browser." That is real usage context rather than nothing. But it never says when NOT to use it, and never mentions reply_to_note or substack_publish_note as the alternative for an agent that wants an action instead of instructions.

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