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

Annotations already declare destructiveHint=true and idempotentHint=true, yet the description adds genuinely new behavior: null clears the billing contact, the one-way status transition rule, and two auth prerequisites (claimed Last Price credential, claimed workspace with a 403 for self-registered sandbox keys). This is exactly the context annotations cannot carry.

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?

Three sentences, front-loaded with the core action and field list, then constraints, then permissions. Dense but every clause carries operational information; the workspace-claim sentence is long but is required context rather than padding.

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 destructive, idempotent mutation with six parameters and no output schema, the description covers the invocation contract, the state constraint, the null-clearing semantics, and both auth gates. Nothing an agent needs in order to call this correctly and avoid a 403 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 coverage is 100%, so the baseline is 3; the description exceeds it by stating the cross-field constraint that at least one of the five mutable fields must be supplied — a rule the schema (which requires only order_id) does not express — and by reiterating the null-clears-contact semantics for billing_contact_id.

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 ('Change an order') and immediately names the fields it operates on, which cleanly distinguishes it from create_order/delete_order/get_order siblings. An agent knows exactly what class of operation this is without opening the schema.

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 states the invocation precondition — pass order_id plus at least one mutable field — and adds the state-transition rule that a non-draft order cannot return to draft. It does not name an alternative sibling (e.g. activate_order, cancel flows) for when this tool is the wrong choice, which keeps it below a 5.

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