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

Annotations only give the generic safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false, idempotentHint=false); the description adds real behavioral detail beyond them: accepted formats (PDF, PNG, JPEG), a hard cap of 20 per proposal, that file_url must be a public https link, and that re-uploading against a requirement overwrites the previous file. It still says nothing about failure modes or async behavior, so it falls short of a full 5.

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?

The definition is compact and information-dense, but the lead sentence spends its effort describing prepare_form rather than this tool, pushing the actual purpose into second position. A reader has to parse a workflow preamble before learning what add_attachment does.

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?

With an output schema present, return values need not be explained, and the description covers the important call-time facts: accepted inputs, format and count limits, requirement matching, replacement behavior, and cost. Remaining gaps are minor (proposal_id provenance, error handling), so it is adequate for a 4-parameter write tool.

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%, so the description must carry the load, and it largely does: file_url is defined as a public https link, file_base64 as the inline alternative, and requirement as the named entry from attachments_required with defined replace semantics. proposal_id is only implicitly identified via 'proposal from prepare_form', leaving one parameter less precisely specified than the others.

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 second sentence states a specific verb and resource: attach one document (file_url or file_base64) to a proposal produced by prepare_form. That is enough to separate it from siblings like compose_pdf or merge_pdf. The opening sentence, however, describes prepare_form's workflow rather than this tool's, which muddies the front of the definition.

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 establishes the precondition clearly: the proposal must come from prepare_form, and the requirement must name an entry in that form's attachments_required list. The replacement rule (a second upload for the same requirement replaces the first) and the cost note give the agent decision context. It never states when NOT to use it or which sibling to prefer for other attachment needs.

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