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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, and the description is fully consistent with them by stating the tool 'opens nothing by itself.' It adds genuine value beyond the annotations by disclosing the shape of the output (screens, buttons, fields) and the fact that no first-party MCP server exists as of a dated check.

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 description is short and front-loads the core behavior plus the handoff to browser tools. The final API-check sentence is somewhat tangential and the middle sentence packs two distinct facts into one clause, but nothing is padded.

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-parameter guide tool with no output schema, the description covers what it returns and what it does not do. A brief note on domain format (e.g., comma-separated, one per line) or on how the returned steps map to the browser tools would close the remaining gap.

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 tool takes zero parameters and the schema is empty with additionalProperties=false, so there is nothing for the description to disambiguate. Baseline 4 applies.

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 the specific resource (excluded domains in the user's Findymail account) and clarifies the actual behavior of the tool: it returns step-by-step instructions rather than performing the action. This distinguishes it from the cotlet_browser_* siblings it tells the agent to use afterward. It falls short of 5 because it never explains what 'excluded domains' are in Findymail's context and the name/title imply a direct mutation that the body then walks back.

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?

There is an implied when-to-use (the user wants to add excluded domains) and explicit sequencing: call this first, then execute with cotlet_browser_* tools. However, it gives no guidance on when to prefer this over the REST API it mentions, nor any prerequisites or exclusions relative to the other findymail_* siblings.

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