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

With no annotations, the description carries the full burden. It discloses key behaviors: creates a session, saves buyer situation (payment, trade-in, timeline), returns a bookmarkable URL, and emphasizes natural data gathering to strengthen the dealer lead. It does not mention potential side effects like overwriting existing sessions, but for a create tool this is sufficient. The added context about the dealer lead goes beyond basic functionality.

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?

The description is a focused paragraph with a clear lead sentence about the core action, followed by supporting behavioral guidance. All sentences earn their place: the URL return value, the benefit to the dealer lead, and the advice to gather information naturally. It is not excessively verbose, though it could be slightly more concise by trimming redundant phrasing.

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 tool with 11 optional parameters and no output schema, the description gives enough operational context: what the session is for, what to save, and the key output (URL). It does not explain how to handle existing sessions or duplicates, but for a create tool this is acceptable. The presence of sibling tools like cars_session_tradein is mentioned in the schema, and the description complements that by setting the session-level context.

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?

The input schema covers 100% of parameters with detailed descriptions, so the baseline is 3. The description mentions payment method, trade-in, and timeline as things to save, which maps to those params, but adds no additional parameter-specific semantics beyond what the schema already provides. The general guidance to gather naturally is useful but does not explain any particular parameter value or format.

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 clearly states the verb and resource: 'Create a personalized car research session for the buyer.' It also distinguishes the tool by noting it returns a unique URL to bookmark and return to, which is a distinctive feature among sibling session tools. The purpose is specific and unambiguous.

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 provides usage context by saying 'As you help the buyer' and guides on how to collect information: 'Don't ask all at once — gather these naturally over the conversation.' This gives clear timing and behavior, though it doesn't explicitly contrast with sibling tools like cars_session_read or cars_session_add_car. The instruction to not interrogate helps the AI agent understand when and how to use this tool.

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