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

Annotations already provide readOnlyHint=false and destructiveHint=false, indicating a non-destructive write operation. The description adds no further behavioral details (e.g., whether attaching replaces an existing contact or is idempotent). Given the annotations, this is adequate but not enhanced.

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 description is a single, concise sentence with no redundant words. It front-loads the action and parameter semantics efficiently, making it easy to parse.

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 simple attach operation, the description covers the core behavior and parameter meaning sufficiently. It does not mention output (none exists) or error cases, but none are critical for invoking the tool correctly. A minor gap is not clarifying whether an existing contact is overwritten, but that is not essential for basic usage.

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?

The schema describes both parameters simply as IDs. The description adds meaningful context by explaining that `client` should be a client ID for money-in documents and a supplier ID for money-out documents, which helps the agent choose the correct value beyond the raw schema.

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 clearly states the action ('Attach a contact to a document') and adds a useful distinction between money-in and money-out documents. It is specific about the verb and resource, and while it does not explicitly name sibling tools, the action is unambiguous.

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 guidance on when to use which contact type ('client for money-in, supplier for money-out'), which helps select the correct parameter. It does not explicitly contrast with the sibling tool `remove_document_contact`, but the intent is clear enough for most use cases.

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