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

With only readOnlyHint=false and idempotentHint=false annotations, the description carries the behavioral burden and does so well: it discloses the return shape, the markdown rendering behavior, the ~1KB reliability limit for contentBase64, and the truncation risk for long string arguments.

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 focused paragraphs with no filler. The core purpose and not-evidence caveat are front-loaded, followed by the return format, integration step, size limitation, and alternative path — every sentence earns its place.

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?

There is no output schema, so the description correctly explains the return object and how to use the markdown. It also covers the size threshold, the fallback upload flow, and the fact that the result shape is the same, making the tool self-sufficient for correct invocation.

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 the baseline is 3. The description adds real value on top by warning that contentBase64 is only reliable for payloads ≤ ~1KB and that larger files must go through goal-request-upload, which is critical for correctly supplying the contentBase64 parameter.

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 opens with a specific verb and resource: 'Attach a small file ... to a GOAL as a description attachment.' It explicitly differentiates from evidence attachments by stating the file is 'NOT evidence,' 'not bound to any acceptance criterion,' and 'never counts toward closing the goal,' which makes it distinguishable from sibling tools like goal-attach-evidence.

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 gives clear when-to-use/when-not-to-use guidance: use this tool for small description attachments, and 'For anything bigger call goal-request-upload.' It also tells the agent how to follow through by pasting the returned markdown into 'goal-update description.'

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