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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds substantive behavior beyond that — only 'active' services are returned, after-hours price appears only 'when the operator set one', and services are flagged as mobile or request-only. It does not say what happens for an unknown slug or an operator with no services, which keeps it below 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 waste: the resource and scope come first, the return shape second, and the invocation constraint last where an agent will look before calling. No repetition of the title or annotations.

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 simple read-only list tool with no output schema, the description carries the necessary burden by enumerating returned fields and conditional values. Missing only edge-case behavior (empty results, invalid identifier) and any pagination note.

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% and both parameters already explain their source, so the baseline would be 3. The description adds a genuine constraint not expressed in the schema — 'exactly one of slug or operator_id' — which is critical since neither parameter is required and additionalProperties is false. It omits what happens if both or neither are supplied.

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 ('Lists the active services of one listed operator') and scopes it to a single operator, which cleanly separates it from search_operators and get_operator. The enumerated return fields make the distinction concrete rather than implied.

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 clear invocation context: exactly one of slug or operator_id, both sourced from search_operators. It stops short of saying when to prefer this over sibling tools such as get_operator or list_availability, but the operator-scoped framing makes that largely self-evident.

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