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

Annotations already flag destructiveHint=true and openWorldHint=true, so the bar is lower, yet the description still adds real context: the 10 MB ceiling, the fact that an existing file at that path is REPLACED, and that the link's page markup is not touched. It stops short of saying whether the old file is recoverable or what happens if two uploads race for the same path.

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 tight sentences with zero filler; the actor-scope ('one file ... by relative path') and the constraint ('Up to 10 MB') are both 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 3-param, no-output-schema, annotated write tool, the description covers what is uploaded, where it lands, size limits and non-effect on the page. The only material hole is content encoding for 'base64' and the lack of any mention of the result of a successful upload.

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 67% and the two documented params (link, path) already carry their examples in the schema; the description adds only the relative-path framing. The undocumented 'base64' param is left unexplained — no hint whether raw base64, a data URI, or a URL is expected, and the 10 MB limit is not tied to it explicitly.

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?

Specific verb (add/replace) plus resource (a single file served by a link at a relative path), with concrete file classes enumerated. It never names or contrasts a sibling such as update_link or send_artifact, so an agent must infer the boundary between 'edit the link' and 'upload an asset to the link' on its own.

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 clause 'that a link loads by relative path, without changing the page' implies the scenario (attaching assets that the link's HTML references), but there is no explicit when-to-use versus update_link/send_artifact guidance and no prerequisites stated. Usage is inferable rather than stated.

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