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

Annotations already mark this tool as destructive and non-idempotent, so the safety profile is covered structurally. The description adds an explicit 'Side effects: modifies multiple outbox records' line, which is consistent but mostly restates the update operation and the destructiveHint. No additional context about irreversibility or permissions is provided.

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 description is two short sentences with the core action front-loaded and the side-effect note immediately following. There is no filler, repetition of the title beyond what is useful, or unnecessary qualification.

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?

The input schema, output schema, and annotations cover most of what an agent needs to invoke the tool correctly. The description covers the operation and side effects, though it could be slightly more explicit about constraints such as whether only queued faxes are eligible or how invalid IDs are handled.

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 schema already documents payload, ids, comment, and user_id. The description's mention of 'multiple' and 'comment' only reinforces the ids/comment fields and does not add meaningful new parameter-level semantics.

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 names a specific verb ('Update'), a specific resource ('outbox faxes'), a field ('comment'), a cardinality ('multiple'), and a batching characteristic ('in one request'). This distinguishes it clearly from the single-item sibling 'update-outbox-fax' and from the broader 'bulk-update-faxes'.

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 gives clear context: use this tool when you need to change comments on several queued outbox faxes at once. It stops short of naming the alternative single-update tool or stating when not to use it, so it lacks explicit exclusion guidance.

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