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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, and the description is consistent with them while adding real value: 'opens nothing by itself' sets the no-side-effect expectation and the return shape (screens, buttons, fields) is described. The 'checked 23 Oct 2026' date conveys the freshness of the API claim, though nothing is said about failure modes if the account or browser session is unavailable.

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 instruction is front-loaded, but the final sentence about Findymail's REST API and the check date is tangential meta-commentary that competes with the actionable steps. The dense semicolon-chained phrasing also makes it slower to parse than necessary.

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 zero-argument, read-only guidance tool with no output schema, the description covers what it returns (the procedure) and what it does not do (perform the action), which is what an agent needs. It leaves minor gaps around prerequisites, such as whether the user must be logged into Findymail first.

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?

Zero parameters with 100% schema coverage, so there is nothing for the description to compensate for and the baseline of 4 applies. The description correctly does not invent argument detail for a no-arg tool.

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+resource (get credits) scoped to the user's own Findymail account, and immediately clarifies that it returns step-by-step instructions rather than performing the action. That clarification is essential because the name alone would suggest a balance lookup, and the description also names the cotlet_browser_* siblings that actually execute the steps.

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?

Explicitly frames the workflow: this tool only returns the procedure, then the agent should act with cotlet_browser_* tools in the user's Findymail Cloud Browser. It also rules out an API alternative by noting no first-party MCP server exists. It stops short of stating when NOT to use it (e.g., versus a direct balance/credits query), but the context is clear enough to route correctly.

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