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

Annotations already declare destructiveHint=true, idempotentHint=false and readOnlyHint=false, so the safety profile is covered structurally. The description adds nothing beyond that: it doesn't say what happens on duplicate names, that a retry may create a second customer, or what state the account ends up in after creation.

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?

A single sentence with no filler. The audience qualifier is front-loaded ahead of the action, which is slightly inverted for scanning but keeps the discriminating condition visible.

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, yet the description never indicates what is returned (presumably a customer id needed for assign_number_to_customer and get_customer_usage) or that all three parameters are optional, meaning a bare customer can be created. Those are material gaps for a create call that other tools depend on.

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 67% (external_id and metadata documented; name not), so the schema does most of the work. The description adds no parameter-level meaning at all — it doesn't clarify what a 'customer' name represents versus the account name, or how metadata is used for attribution. Middle baseline is fair.

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 ('create a customer') plus the actual function: attributing numbers, messages and usage. It also scopes the audience ('Platforms sending for other businesses'), which no sibling name conveys. It stops short of distinguishing itself from lookalikes such as create_contact or upsert_contact.

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 'platforms sending for other businesses' clause implies the account type that needs this tool, which is useful conditional context. But it never says when not to use it, nor does it point to update_customer for existing customers or create_contact for end recipients, leaving the agent to infer routing among ~100 siblings.

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