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

Annotations already disclose that the tool is not read-only, not idempotent, not destructive, and closed-world. The description adds context about the caller (upload widget) but does not explain what happens on save, such as overwrite behavior or return values, which would be valuable for a mutation tool.

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 short sentences with no wasted words. The critical exclusion is prominent and the context is front-loaded.

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 simple two-parameter internal tool with fully documented schema and annotations, the description is largely complete. The main gap is what happens to the saved image and whether it can be retrieved later, but that is a minor omission given the internal-only purpose.

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 both parameters (filename and data_base64) are fully documented in the schema. The description provides no additional parameter meaning, making the baseline score appropriate.

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 identifies the tool as an internal save operation for the upload widget, specifically for the file the user picked. It distinguishes itself from sibling tools like spur_save_image and spur_upload_image by stating it is not for the assistant, making its scope understandable.

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 explicit exclusion 'Not for the assistant' gives clear guidance on when not to use this tool, which is the key usage decision an AI agent needs to make. It does not name the correct alternative for the assistant, but the exclusion is sufficient to prevent misuse.

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