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

With no annotations, the description carries the full behavioral burden and does a good job of it: it discloses the core computation rule (alternating A/B), the default interval (15,000 km or 12 months, whichever comes first), and the inputs the estimate depends on. It does not describe the shape of the result or how partial/ambiguous inputs are handled, which keeps it 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, no filler. The purpose and computation basis come first and the default interval constraint is front-loaded immediately after, so the most decision-relevant facts are read first.

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 stateless estimation tool with no annotations and no output schema, the description supplies the algorithm and defaults an agent needs to call it correctly. It leaves the return value's structure implicit, which is a minor omission given there is no output schema to cover it.

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%, so the schema already documents all six parameters including the 15,000 km and 12-month defaults. The description restates those same defaults rather than adding syntax or semantics beyond the schema, 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?

The description names a specific verb (estimate) and resource (next Mercedes-Benz service) and even specifies the underlying model: alternating Service A/B, ASSYST-style, computed from last service type, date and mileage. That is precise enough that an agent knows exactly what the tool returns conceptually, and no sibling (explain_service, find_specialist, warning_light_info) overlaps with this calculation.

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 only implied: you supply last service data to get the next service estimate. The description never states when to prefer this over alternatives or any preconditions (e.g. what to do if the last service type is unknown). Since no sibling performs a comparable estimate, the missing 'when-not' guidance is a modest gap rather than a fatal one.

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