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

Beyond annotations, the description discloses key behavioral traits: small images return viewable content, larger ones return metadata, and `savePath` writes exact bytes to disk. The limitation about .fig containing no rendered frame pictures is valuable and prevents misuse. It does not contradict the annotations.

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 dense sentences carry all essential information with no filler. The core action and input modes are front-loaded, and the limitation is saved for last. Every sentence earns its place.

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 sparse annotations, the description carries the full burden and covers retrieval modes, output behavior, and limitations. The only minor gap is not defining the size threshold between 'small' and 'large' images, but this does not prevent correct invocation.

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%, so the baseline is 3, but the description adds substantial meaning: hash is a 40-hex id reported by fig_node/fig_style, guid resolves to image fills on the node, and hash can be the literal "thumbnail". It also explains the practical difference between inline results and savePath, which the schema alone does not convey.

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 a specific verb (Fetch) and resource (bitmap stored inside the .fig), and clarifies scope with the note that it cannot screenshot a design. It also distinguishes itself from fig_render via the explicit limitation. An agent knows exactly what this tool does.

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 gives clear mode-selection guidance: use `hash`, `guid`, or `hash:"thumbnail"` depending on what is known, and `savePath` for exact bytes versus inline content. It also warns against using it for screenshot-like rendering. It does not explicitly name sibling alternatives, but the practical usage contexts are well covered.

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