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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the mutation profile is partly covered. The description adds a genuine auth prerequisite (customer login), which is real context beyond the annotations, but it says nothing about whether the change is reversible, what happens to the unset field, or error behavior.

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 short sentences, front-loaded with the action and followed by the prerequisite; nothing is padded. The second sentence is slightly vague ('Happy Hamper login') but earns its place as an auth hint.

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?

This is a mutation tool with no output schema and an under-specified schema (no required fields), yet the description covers none of the consequential details: partial-update semantics, what a success response contains, or failure modes. For an update operation it leaves too much to inference.

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?

At 50% schema coverage only 'phone' is documented (as a US number), and the description merely restates the two parameter names. Critically, the schema marks zero required parameters while the description says 'name or phone', leaving the agent unsure whether at least one must be supplied — a gap the description should close and does not.

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 ('Change') and precise resource ('customer's name or phone number'), which implicitly separates it from update_address and update_subscription among the siblings. It does not name an alternative explicitly, but the scope 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?

The description gives a prerequisite ('Needs the customer's Happy Hamper login') but never says when to reach for this versus update_address or get_account, nor any exclusion. Usage is only implied by the resource name.

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