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

Beyond the readOnlyHint and idempotentHint annotations, the description discloses that the URL is both 'secret' and 'short-lived', signaling the caller to treat it as sensitive and time-sensitive. It also clarifies that the tool returns a URL rather than the object bytes, which prevents a mistaken expectation of binary download. No contradiction with 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?

A single sentence with no filler, front-loading the action and the two critical qualifiers ('secret', 'short-lived'). Every word adds value.

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 three fully documented required parameters, the description covers the core behavior. The only gap is the absence of any usage alternative guidance, but that belongs to the usage dimension; operationally nothing needed to invoke the tool correctly 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%, so the baseline is 3; the description adds no parameter-level detail beyond what the schema already documents. The tool's three parameters are fully described in the schema, including examples for object_key and bucket_name.

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 uses a specific verb ('Return') and resource ('a secret, short-lived GET URL for an object's bytes'), clearly distinguishing it from metadata, upload, or delete operations. It doesn't name sibling tools explicitly, but the URL-returning behavior sets it apart.

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 implies use when a URL is needed rather than the bytes themselves, but it offers no explicit when-to-use guidance or exclusions relative to siblings like get_object_metadata or upload_object. There is no mention of alternatives, so the agent must infer context from the sibling names.

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