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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so 'side effects: none (read-only)' earns no credit and is redundant. The real addition is the eventual-consistency warning that a 404 right after send-fax-uploaded may mean the record is not yet visible rather than a failed send — behavior an agent could not infer from 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?

Front-loaded with the core purpose in one clause, followed by the timing caveat. The final 'Side effects: none (read-only)' sentence is wasted space given annotations already say this.

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?

An output schema exists and parameters are fully described, so the description only needs to orient the caller — which it does, including the one non-obvious failure mode. Only the explicit relation to get-fax and list-outbox-faxes is 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%; both user_id (default self) and outbox_fax_id are already documented in the schema. The description adds no format, ID source, or defaulting detail beyond that, so baseline 3 applies.

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 and resource ('Get details of a fax scheduled for sending (outbox)'), and the parenthetical '(outbox)' distinguishes it from the sibling get-fax, which returns sent faxes. It never names get-fax explicitly, so the differentiation is implied rather than stated.

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 404-after-send-fax-uploaded note gives a concrete usage context tied to a named sibling, which is genuinely helpful. However, it does not tell the agent when to prefer this over list-outbox-faxes or update-outbox-fax, and offers no exclusions.

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