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

With no annotations, the description must carry the burden of behavioral disclosure. It states the two main actions: verifying file existence and creating a file block. This is transparent about the core mutation. However, it does not disclose failure behavior (e.g., what happens if the file doesn't exist), idempotency, or whether it returns any value. These gaps leave some behavioral ambiguity, but the description is not misleading.

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 sentences with no fluff. The first sentence states the purpose, and the second gives a clear usage instruction and additional action. It is front-loaded and efficient, earning every word.

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 description covers the key aspects: when to call and what it does. However, it lacks information about return values (no output schema) and potential failure conditions. For a tool that performs a verification step, the agent might need to know what happens on success or failure, but this is not provided. Given the simplicity of the operation and the explicit flow reference, it is moderately complete.

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 coverage is 100%, so all six parameters are already described in the schema. The description adds contextual value by linking s3_key and file_id to get_upload_url, but this is also mentioned in the schema descriptions. It doesn't add new meaning beyond reinforcing the relationship, 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 clearly states the tool's purpose: confirming a completed file upload and creating a database record/file block. It specifies the verb 'confirm' and the resource 'completed file upload', and distinguishes it from siblings like get_upload_url by referencing the presigned URL step. It doesn't explicitly contrast with create_block, but the phrase 'file block' makes the specialization clear, so it's a specific action.

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 explicit when-to-use guidance: 'Call this after successfully uploading a file to the presigned URL from get_upload_url.' This sets a clear precondition and implies not calling before upload. It doesn't mention alternatives, but the direct reference to the previous step in the flow is sufficient guidance for correct usage.

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