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 reconciles the seemingly mutating name with that safety profile by stating the tool 'opens nothing by itself.' It adds genuinely useful context beyond annotations: the return content is procedural UI guidance, and no public API exists so the browser tools are the only execution path. It does not describe response length or failure modes, which keeps it short of a 5.

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?

Three sentences, all carrying information, with the key constraint ('opens nothing by itself') placed early. The closing sentence is slightly redundant in its phrasing ('CoachingPortal's official API: CoachingPortal publishes no public API'), which costs a point but not readability.

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, non-destructive tool with no output schema, the description covers everything an agent needs: what is returned (step-by-step screens/buttons/fields), that nothing is executed, which tools complete the task, and why (no public API). The non-obvious two-step retrieval-then-browse pattern is fully explained.

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 a closed empty object, so there is nothing for the description to disambiguate. Baseline for a zero-parameter tool is 4, and nothing here misleads about inputs.

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 makes clear the tool returns a step-by-step procedure (screens, buttons, fields) for uploading a progress photo in the user's own CoachingPortal account, rather than performing the upload. It also distinguishes itself from the cotlet_browser_* tools that actually execute the action. The one blemish is that the opening clause 'Upload progress photo...' momentarily reads as if the tool performs the write, which is only corrected in the next sentence.

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 explicitly states the handoff pattern: this tool 'opens nothing by itself', and the agent should then 'do it with the cotlet_browser_* tools in the user's CoachingPortal Cloud Browser.' That is a clear when-to-use and what-to-do-next statement. It does not state any exclusion such as 'do not use this if you already know the workflow', but the routing guidance is concrete enough to act on.

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