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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds genuine value beyond that by listing the data a caller gets back (balance, credit limit, points, custom fields), which matters because there is no output schema. It does not mention behavior on a missing/unknown person_id, so it stops short of a 5.

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 sentences, zero filler, with the identifying scope front-loaded and the returned fields following. Every clause earns its 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?

For a single-parameter read-only lookup with full schema coverage, the description covers what the tool returns and which identifier it keys on. Only edge-case behavior such as not-found handling is absent, and that is a minor gap rather than a blocker.

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 schema already explains that person_id is the customer person id and how to obtain it. The description only restates 'by person id' with no added format or constraint detail, so the baseline 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 specific verb and resource ('One customer by person id') and enumerates exactly what the call returns (contact details, tier, tax settings, balance, credit limit, points, notes, custom fields). That distinguishes it cleanly from phppos_list_customers without 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?

The single-customer phrasing implies a detail-lookup use case, but the description never says when to use this instead of phppos_list_customers or phppos_update_customer. The only routing hint (how to find person_id) lives in the schema description, not here.

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