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

Annotations declare readOnlyHint=true (upper-scope readable safety), and the description adds useful transient context: image_id valid for 5 minutes — a meaningful expiry constraint. However, it doesn't disclose whether uploads persist, are deleted after processing, or what failure behaviors occur. With readOnlyHint already covering the safety profile, the added expiry context earns a 3.

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 tight sentences with zero filler. State purpose, return contract, consumers, and usage threshold in under 40 words. Every clause carries information.

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 an output schema present and 100% param coverage, the description needn't document return format. The description covers purpose, transient validity, downstream consumers, and the size threshold — adequate for a simple upload tool. Minor gap: no error/limit info (e.g., max file size) but that's acceptable given the tool's simplicity.

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%, but the description adds meaning by explaining the ephemeral output contract and naming the two consumers. Notably, the image_base64 parameter description adds a size-limit clarification ('No size limit here (unlike palette_extract's image_base64)') that clarifies cross-tool constraints. The description reinforces how to pass image_id downstream.

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 clearly states a specific verb (ingest/upload) + resource (image to Colour Memory for ephemeral processing), and explicitly names the downstream tools (palette_extract, image_brief) that consume the result. It distinguishes its purpose from siblings by defining it as the entry-point upload tool.

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?

States when to use (any image over 50 KB) and names the consuming tools (palette_extract, image_brief), implying it's the prerequisite step. However, it doesn't state when NOT to use it or explicitly name alternatives for the opposite case (small images), though the size threshold implies a heuristic.

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