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

Annotations already declare readOnly=false, idempotent=false, destructive=true, so the write nature is covered. The description adds genuinely new behavioral context: explicit absence of side effects (no charge/invoice/email), the returned customer_id, and the external_key uniqueness constraint — all beyond the annotations.

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?

Front-loaded with 'WRITE:' and packed into a few high-signal clauses with zero filler. Side-effect exclusions, return value, uniqueness, and the sibling call are all stated tersely.

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 19-param mutation with no output schema, the description covers the missing return value (customer_id), the safety-relevant side-effect profile, and the de-duplication prerequisite. Nothing an agent needs to invoke it correctly is absent.

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 earns above baseline by explaining that the superuser_* fields collectively add a primary contact (grouping intent the schema lists individually) and by flagging external_key as a unique, non-reusable key.

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+resource ('create a new customer') and leads with a 'WRITE:' marker. The parenthetical scope note and the reference to chargeover_list_customers / chargeover_update_customer siblings make it unambiguous which tool to pick.

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 prerequisite ('Use chargeover_list_customers first to avoid a duplicate') and clarifies what this call does NOT do (no charge, invoice, or email). It stops short of stating when to prefer create vs update_customer, but the de-duplication guidance is concrete.

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