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

Annotations only supply destructiveHint=true; the description goes further by spelling out the concrete destructive behavior (the contacts array overwrites the existing list) and flags this as a write. It does not cover permission requirements or whether omitted fields (first_name, last_name, summary) are left unchanged, so it stops short of full behavioral disclosure.

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 with the 'WRITE:' marker front-loaded, then the destructive-contact warning, then the API mapping. Every sentence carries distinct information and none repeats structured fields needlessly.

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 5-parameter mutation tool with no output schema, the definition covers the write nature, the destructive contacts behavior, sibling routing, and the endpoint. Gaps remain around permissions, partial-update semantics for omitted fields, and whether a bare `id` with no other fields is a no-op error, but the essentials are present.

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 60%, and the description's only added parameter insight is that `contacts` replaces the list — which the schema already states nearly verbatim ('replaces the existing one'). Fields like `id`, `first_name`, and `last_name` carry no description, but the enum-less nested contact shape is at least documented in the schema, so baseline 3 is warranted.

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 ('update a customer'), leads with a 'WRITE:' marker, and even names the underlying Enchant REST call (PATCH /customers/{id}). The sibling-routing sentence plus the distinct write semantics let an agent separate this from enchant_get_customer, enchant_list_customers, and enchant_add_customer_contact without opening a 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?

Gives an explicit conditional rule: if `contacts` is supplied it REPLACES the list, and directs the agent to enchant_add_customer_contact when the intent is to add a single contact. That names both the alternative tool and the condition that selects it, leaving nothing to inference.

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