Add a vehicle to the buyer's shopping session. Include a fit score (1-10) and notes explaining why you recommend it.
| Name | Required | Description | Default |
|---|---|---|---|
| vin | Yes | 17-character VIN of vehicle to add | |
| notes | No | Why you recommend this vehicle | |
| score | No | AI fit score 1-10 (how well it matches preferences) | |
| session | Yes | Session hash | |
| agent_id | No | Your agent identifier |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must disclose side effects. It only says 'Add' and gives parameter guidance, without mentioning whether this modifies session state, requires permissions, is reversible, or what the response/return value looks like. For a mutating tool this is a notable gap.
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, front-loaded with the verb and object, and no redundant or vague content. It directly tells the agent what to do and what to include.
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 low-complexity add operation with full schema coverage, the description is nearly sufficient. However, it lacks any mention of output, success/failure behavior, or session state consequences, which would be more important because no output schema or annotations exist.
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 input schema already documents all five parameters. The description adds no new meaning beyond restating score (1-10) and notes (why you recommend), which matches the schema descriptions. 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?
Description uses a specific verb ('Add') and resource ('a vehicle to the buyer's shopping session'), clearly distinguishing it from sibling tools like compare, interest, or tradein. It also mentions the key inputs (fit score, notes) that make the tool's purpose unmistakable.
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 description gives clear context: use when adding a recommended vehicle to an active buyer session. It does not explicitly name alternatives or exclusions, but the action is unambiguous and distinct from the sibling session tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Most tools target distinct resources (dealer inventory, vehicle search, session actions), but cars_session_message and cars_session_reply have overlapping purposes as both involve posting messages. The session tools are otherwise clearly differentiated by their action verbs.
All tools share the 'cars_' prefix and use snake_case, but the verb-noun pattern is inconsistent: some are action-first (cars_search, cars_session_create) while others are noun-only (cars_vehicle, cars_dealers, cars_history). Session tools follow a consistent 'session_<verb>' structure, but the broader set mixes conventions.
With 19 tools, the set is on the heavy end, falling in the 16-25 range that feels borderline. The count is justified by the comprehensive session workflow, but it approaches the threshold where tool selection becomes cumbersome.
The core journey of searching, inspecting, and tracking vehicles through sessions is well covered, including dealer communication and trade-in. However, there are notable gaps: no way to remove a vehicle from a session or update general buyer profile details (payment method, timeline) after initial creation.