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

Annotations already indicate this is a non-read-only mutation. The description adds important behavioral context: it returns a presigned URL, requires a separate raw-byte upload, and depends on finalize_upload for commit. This goes beyond the annotation's binary safety flags and clearly explains the two-step workflow.

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?

Two sentences, no filler. Front-loaded with the core action and a clear cap on size, followed by the essential next step. Every word contributes meaning.

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 6-parameter mutation tool with no output schema, the description covers the critical flow: how to upload (presigned URL) and how to complete (finalize_upload). It does not mention error cases (e.g., lock conflicts, version mismatches), but those are partially documented in the parameter descriptions. Overall, it gives enough context for an agent to correctly invoke the tool.

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 already describes all 6 parameters with 100% coverage, so the baseline is 3. The description adds value by stating the 1 GiB upload limit (clarifying the `size` parameter) and the binary nature (informing `mime_type`), which slightly exceeds the schema's generic descriptions.

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 clearly states the tool starts a large or binary file upload (up to 1 GiB) and returns a presigned PUT URL. It distinguishes itself by mentioning the follow-up finalize_upload step, and implies a contrast with simpler write operations for small files.

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 usage context: use for large/binary files, then call finalize_upload to commit. However, it does not explicitly name alternatives (e.g., 'use write for small files') or state when not to use this tool, so it stops short of a 5.

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