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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered without the description. The description adds useful scope disclosure (it returns notes and refund history, unlike the list) but says nothing about the return shape or how large a customer record can be, so it only modestly exceeds the annotation bar.

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 tight sentences, zero filler, and the highest-value fact (what the tool returns) is front-loaded in the first clause. The two constraints that follow — ID source and when to call — each earn their place.

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?

There is no output schema, so the description carries the burden of telling the agent what comes back, and it does enumerate the key fields (addresses, notes, order count, spend, refunds). What is missing is any note on result size or whether the record is a flat object, but for a single-parameter read tool this is close to sufficient.

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 100% and the single parameter is already documented as 'Customer id from get_customers — not a name'. The description restates the same constraint ('Takes the customer ID from get_customers, never a name'), which reinforces but does not extend the schema. Baseline 3.

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 (get) and resource (ONE customer) plus the exact payload it returns: addresses, notes, order counts, spend and refunds. The word 'ONE' and the pointer to 'the list' distinguish it from the sibling hub_get_customers without the agent opening either 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 explicit timing guidance ('use it before answering a question about a specific person') and justifies it by contrast with the list, which 'leaves notes and refunds out'. It does not name hub_get_customer_orders, hub_get_refunds, or hub_get_transactions as narrower alternatives, so routing among the per-customer siblings is left partly to inference.

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