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

readOnlyHint=true already tells the agent this is a safe read, and the description goes beyond that by disclosing the shape of what comes back (booking history, cancellations/no-shows, membership, store credit). It does not cover error behavior (e.g. unknown id) or rate/permission constraints, so it stops short of full transparency.

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 tight sentences, front-loaded with the operation and its returned fields; the trailing 'Bookeo: GET /customers/{id}' is mildly redundant but usefully anchors the endpoint. No filler.

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?

With no output schema, the description carries the burden of describing returns and does so by enumerating the customer data fields. For a one-parameter read tool this is nearly complete; only error/not-found behavior is unaddressed.

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?

There is a single parameter whose schema description coverage is 100%, so the schema already fully documents 'id'. The description adds no format or sourcing guidance for that id, so the baseline of 3 applies.

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 precise verb+resource ('Get one customer') and enumerates the returned data (contact details, bookings, cancellations/no-shows, membership, store credit), which cleanly separates it from bookeo_list_customers and bookeo_update_customer. It stops short of naming those siblings, so the differentiation is implicit rather than explicit.

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?

Usage is implied: fetch a single customer when you already have the id, as opposed to bookeo_list_customers or bookeo_search_matching_slots. However, no when-to-use/when-not-to-use conditions, no prerequisites, and no alternative is named, so the agent must infer the routing.

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