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

Annotations already cover read-only, idempotent, non-destructive, closed-world, but the description adds substantial non-obvious behavior: the result is a reduced copy (max 512px on the long side) with metadata stripped and is NOT the stored file, and every view is written into the document's agent change record so reviewers see what was read. It also discloses the admin-enablement dependency. This is exactly the kind of context annotations cannot carry.

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?

Front-loaded with the action, then inputs, then return shape, then side effects, then the gating condition. Every sentence carries distinct information with no restatement of the name or title.

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?

There is no output schema, so the description must, and does, specify the return payload (reduced image, name, size, full dimensions) as well as the audit side effect and availability gating. Nothing an agent needs to invoke it correctly appears to be missing.

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 100%, so the baseline is 3. The description still adds value by showing the expected src format inline ('') and by tying 'crop percentages' to the returned full dimensions, clarifying how src relates to the cursor/crop context. No further syntax or edge-case detail is given.

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?

Specific verb ('Look at') plus resource ('an image in a document') and immediate scope qualifier ('a document you can read'). It is clearly distinct from the sibling traceable_image_upload (view vs. upload) and traceable_doc_read, so an agent can route without opening a schema.

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 a precondition ('Only an image the document holds can be viewed'), the correct input convention ('src exactly as a read of the document shows it'), and an environmental gate (admin must enable the tool under Org settings > Releases when controlled releases are on). It does not name an alternative sibling for the case where the image must be uploaded first, so it stops short of full routing guidance.

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