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

With no annotations, the description carries the full behavioral burden and discloses important traits: 5MB size limit, one-day auto-expiry, key-only readability, auth requirement, and no billing. It does not specify URL TTL or failure behavior for oversized uploads, but the main constraints are covered.

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 front-loaded with the core action and immediately explains the two-step handoff and constraints. Every sentence contributes operational or behavioral detail without wasteful repetition.

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 presigned-upload helper with no output schema and no annotations, the description supplies the return values (URL and upload_id), the follow-up flow, key limits, expiry, auth, and billing context. An agent has enough information to invoke it and use the result correctly.

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?

The schema has 100% description coverage for the single content_type parameter, including examples and the default. The description adds no parameter-specific semantics beyond what the schema already provides, so the baseline of 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?

The description states a specific verb and resource: get a presigned S3 PUT URL for uploading a file. It also identifies the upload_id handoff to a consuming endpoint, so the tool's role is unambiguous among unrelated siblings.

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?

It gives a clear operational flow: call this tool, PUT the file to the returned URL, then pass upload_id to the consuming endpoint. It does not explicitly name when not to use it or alternatives, but no sibling appears to overlap with this upload capability.

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