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

Beyond the annotations (all of which it is consistent with), the description discloses two things an agent could not otherwise know: cost ('Every started minute of the session costs credits') and session lifecycle ('ends when closed or 3 minutes after the last call in that browser'). For a metered, session-bound tool this is exactly the right kind of added context.

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?

Two dense sentences; the core output is front-loaded before the cost/lifecycle caveats. The colon-introduced list ('boards, canvases and layouts') is slightly awkward but each clause carries real information rather than restating the title.

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 output schema and no parameters, the burden falls on the description, and it covers output form, cost, and timeout. It does not state prerequisites (an active browser session) or what happens when no browser is connected, which is the main remaining gap for a session-scoped tool.

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 no parameter semantics are required — the baseline for a parameterless tool applies. The description correctly adds nothing spurious 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 names a specific verb and resource ('Returns a JPEG image of the visible part of the current page') and even flags the return payload as URL + title. The clause 'boards, canvases and layouts that the page text does not show' indirectly distinguishes it from cotlet_browser_read, but it never names that sibling, so the differentiation is inferred rather than stated.

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?

The phrase 'that the page text does not show' gives a usable heuristic for choosing screenshots over the text-reading sibling. What is missing is an explicit instruction such as 'use cotlet_browser_read for text' or a note that a browser session must already be connected via cotlet_browser_open/connect.

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