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

Goes well beyond the annotations (readOnly=false, destructive=true, openWorld=true) by disclosing the invitation email side effect, that the optional address becomes the default service address, that duplicate emails are rejected, and — most importantly — that the call 'waits for the owner's approval.' That pending-approval state is a behavioral trait an agent would otherwise not know. It stops short of describing what happens to partial failures or how long approval takes.

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-loads the core action, but the invitation email is explained twice ('BookingKoala emails them an invitation to set a password' and again 'BookingKoala emails the customer at once to set a password for the store's booking page'), and the 'as Add Customer in the admin does' clause is filler. Roughly a third of the text could be cut with no loss.

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 12-parameter creation tool with full schema coverage and annotations present, the description covers the main things an agent needs: the email side effect, duplicate-email refusal, default-address behavior, the approval gate, and the return shape (via get_customer). It lacks any error taxonomy beyond duplicate email, but nothing critical 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 schema already documents all 12 parameters and the baseline is 3. The description adds one genuinely new fact — that the supplied address becomes the customer's default service address — but otherwise repeats the email/invitation semantics already present in the schema, so value beyond the schema is modest.

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 ('New customer in the store'), and the closing line ties it to get_customer, so an agent can tell it apart from get_customer/list_customers without opening a schema. The phrasing 'Adds a customer as Add Customer in the admin does' is circular and adds nothing, which keeps it from a 5.

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?

Offers concrete preconditions (an email already in the store is refused) and an explicit instruction ('use their real address'), which is real usage guidance. However it never states when to reach for this versus list_customers/get_customer, nor what to do after the call returns (e.g. that the record won't be active until approved) — guidance is implied rather than laid out.

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