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

Beyond the annotations (which already flag destructive/openWorld/non-idempotent), the description discloses the return value ('Returns the URL and title'), hard limits (up to 10 files, 20 MB each), and the session billing/lifecycle model ('every started minute ... costs credits; ends 3 minutes after the last call'). That is exactly the extra operational context annotations cannot express.

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?

Three tight sentences, front-loaded with the core action, followed by input formats, limits, and session cost. Dense but every clause carries operational information; nothing is wasted, though the session-credit sentence slightly crowds the core definition.

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 destructive write tool with an open-world browser context and no output schema, the description covers inputs, limits, return value, and session lifetime well. Minor gaps remain around failure behavior (what happens if the element is not a file input or a file exceeds limits), but the agent has what it needs to invoke it 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?

Schema coverage is 100%, so baseline is 3. The description still adds value by explaining the two mutually exclusive file-reference shapes ({url} for online files vs {file_id} for files already in Cotlet) and by clarifying that 'element' is the element's number in the page element list, reinforcing the schema's intent.

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 ('Puts files into a file field of the current page ... or into the file picker an upload button opens'), which is far more precise than the bare title. It implicitly distinguishes itself from the sibling cotlet_upload_file by noting that file_id refers to a file 'uploaded to Cotlet first', but it never names that sibling outright.

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 describes the two invocation contexts (direct file field vs. upload-button picker), which gives useful context for when this tool applies. However, it does not explicitly say when to prefer cotlet_upload_file over this tool or what preconditions (e.g. an open browser session on the right page) must hold, leaving the agent to infer the boundary.

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