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

The description explicitly discloses that no Xero change happens until a human approves, that the approval link is in the response's approvalUrl field, and that the agent cannot approve it itself. It also states the partial-update behavior: only provided fields change. These details go well beyond the annotations and are essential for correct use.

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 front-loaded with the core purpose and each sentence covers a distinct operational fact: approval requirement, approvalUrl location, contactId source, and field-change semantics. There is no filler or redundancy.

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?

Despite having no output schema, the description provides enough context for correct invocation: it explains the pending-change workflow, the approval mechanism, the required source for contactId, and the at-least-one-field constraint. An agent can confidently select and call this tool without needing additional undocumented details.

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 meaningful cross-parameter guidance by requiring at least one of name, emailAddress, or phone, and by reinforcing that omitted fields remain unchanged. This supplements the per-field schema descriptions.

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 'Proposes a change to an EXISTING Xero contact', giving a specific verb and resource while distinguishing it from create_xero_contact. It further clarifies that this tool queues a pending change rather than directly mutating Xero, making its role 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 clearly states when to use the tool: for existing contacts, with contactId sourced from list_xero_contacts, and requiring at least one of name, emailAddress, or phone. It does not explicitly name alternatives like create_xero_contact for new contacts, but the emphasis on 'EXISTING' and the approval workflow makes the intended usage clear.

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