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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the trailing 'Read-only.' adds nothing. Beyond that, it earns credit by describing exactly what comes back with no output schema present — PNG URL at exact 1x pixels, the &frame=N trick for other frames, and what include_pixels adds. It omits error/expired-session behavior.

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 return contents are front-loaded in the first clause and the optional-pixel behavior follows. It's dense but earns most of its words; the closing 'Read-only.' is redundant with the annotations and could be dropped.

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, the description carries the return-shape burden well by enumerating every field and explaining the frame URL convention. A read-only tool with a two-parameter schema needs little more, though failure modes for an invalid or expired session_id are unaddressed.

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?

Schema coverage is 100% and both parameters are documented there, including that session_id accepts an edit link. The description restates those semantics and adds the &frame=N URL hint, but that hint is about the returned URL, not a parameter, so it doesn't materially extend parameter meaning.

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?

A specific verb plus resource: returns the current state of a SpriteForge edit session, and it enumerates the returned content (preview image, size, palette, edit count, PNG URL, optional index grid). This clearly separates it from the mutation/editor siblings like open_editor and save_art.

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?

Usage is implied rather than stated: 'Returns the current state' suggests inspection, and the include_pixels clause hints at when to ask for the grid. But it never names an alternative such as load_art or states when not to use this tool, and gives no guidance on session availability or missing sessions.

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