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

Annotations already declare readOnlyHint=true and destructiveHint=false; the description usefully reinforces this with "opens nothing by itself", which tells the agent no state changes occur on invocation. It also discloses the return shape (sequential instructions) and the follow-up dependency on browser tools. Nothing contradicts the annotations, though it could note prerequisites such as the Cloud Browser needing to be open.

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 the action, then the mechanism, then the API rationale. Each of the three sentences earns its place, though the third sentence is long and carries a parenthetical verification date ("checked 8 Nov 2026") that is more verbose than this zero-param tool strictly requires.

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 carries the full burden and does explain what comes back (step-by-step screens, buttons, fields) and what to do next. Remaining gaps are minor: no mention of authentication state or what happens if no browser session exists.

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, so the baseline is 4 and there is nothing for the description to disambiguate. The schema is fully closed (additionalProperties false) and the description introduces no parameter-like concepts an agent might mistakenly try to pass.

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 ("Mark invoice paid") scoped to "the user's own Invoice Simple account", and immediately clarifies the critical nuance that it returns step-by-step instructions rather than performing the write. That distinguishes it from sibling mutators like invoice_simple_send_invoice or invoice_simple_create_invoice. It stops short of naming a specific sibling it replaces, so it is not a 5.

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?

Gives real workflow guidance: call this to get screens/buttons/fields, then "do it with the cotlet_browser_* tools in the user's Invoice Simple Cloud Browser." It also preempts the API alternative by stating Invoice Simple publishes no public API. However, it never contrasts with the adjacent cotlet_app_guide or cotlet_apps tools, and gives no when-not-to-use condition, so the routing guidance is implied rather than explicit.

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