Attach a file to a card

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

With no annotations, the description carries the burden well: it discloses size caps (100 MB via path, 10 MB decoded for base64), that the app copies the local file in, and that unsafe filename characters are replaced. It doesn't state permission requirements or whether re-attaching the same name replaces an existing attachment.

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?

A single front-loaded paragraph that enumerates the two modes as (1) and (2), then closes with return shape and the cover-image follow-up. Every clause adds information; nothing is redundant.

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 5-param, non-annotated tool with no output schema, the description still tells the agent the source modes, size limits, encoding choices, filename handling, and the returned fields ({ id, filename, mime, size, boardId }). Nothing needed to call it correctly is missing.

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 0%, and the description compensates almost fully: `path` is defined as an absolute local path, `content`/`filename` as inline data, `encoding` defaults to utf8 with base64 for small binaries, and the extension drives the MIME type. Only `cardId` is left implicit, which the purpose line makes obvious.

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?

States a specific verb and resource ('Attach a file to a card') and immediately frames the two sourcing modes. It is clearly distinguishable from the sibling kanbini_delete_attachment and from unrelated card mutations like kanbini_update_card.

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?

Explicitly says 'from ONE of two sources' and gives the selection rule for each: `path` for files already on disk, inline `filename`+`content` for data the agent produces itself. It also names the follow-up route to kanbini_update_card for setting a cover image.

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