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

Annotations already declare the safety profile (readOnly=false, destructive=false, idempotent=true). The description adds a size cap and return value, but doesn't cover retry semantics for idempotencyKey, failure modes, or what happens to orphaned uploads — modest added value over 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?

Two short sentences, front-loaded with the constraints an agent needs before calling. No filler.

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?

For a 3-required-param mutation with no output schema and low schema coverage, the description covers formats, size, and return but leaves the base64 parameter and target-document context unexplained, which is the main remaining gap.

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 only 33%; only idempotencyKey is documented in the schema. The description hints at mime via the format list but says nothing about the required base64 parameter (encoding, content expectations) or how the size limit maps to base64 maxLength.

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?

States a specific verb (upload) and resource (image), with concrete constraints: formats and 5 MiB cap, plus return value assetId. It is clearly distinguishable from siblings like list_images.

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 by the verb, but the description never says when to use this versus list_images or how it relates to a document/site workflow. No exclusions or prerequisites (auth, upload target) are stated.

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