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

Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, so safety signaling is covered. The description adds little beyond the basic action: it does not explain whether existing fills are overwritten, whether the operation is reversible, or what a successful result looks like.

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 single sentence is concise and front-loaded, with no wasted wording. However, for a destructive tool with three undocumented parameters, the extreme brevity leaves the definition under-specified rather than appropriately sized.

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?

Given the tool mutates fills, has no output schema, and has 0% schema description coverage, the description is too sparse. It should at least clarify the built-in pattern format, color behavior, and whether existing fills are replaced.

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 description coverage is 0%, so the description must carry parameter meaning, but it does not mention the color or shape_ids parameters at all. 'Built-in pattern' hints that the pattern parameter expects a built-in pattern name, but format, valid values, and required shape_ids usage remain undocumented.

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 ('Fill') and resource ('shapes') with a clear modifier ('built-in pattern'), making the tool's basic action understandable. It does not explicitly differentiate this tool from sibling fill tools such as set_gradient or set_style, which keeps it from 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?

The description offers no guidance on when to use this tool versus alternatives like set_gradient, set_style, or set_filter. It implies the tool is for applying pattern fills, but gives no conditions, prerequisites, or exclusions to help an agent choose correctly.

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