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 so: it discloses that every line has a source and confidence, that unknowns become ranges, that payments is null, that states outside the 8 covered return a low-confidence estimate without tax and government fees, and that inputs are not stored. It also sets accuracy expectations ('not an offer, not a quote, not penny-accurate').

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 dense but front-loaded: the core purpose, the covered scope, and the produced lines come first, followed by output-field guidance and alternative routing. Every sentence carries information, though the middle section on output fields is packed tightly and could be marginally streamlined.

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 13-parameter tool with no annotations and no output schema, the description covers purpose, inputs' effect (trade-in, buyer location), return structure (itemized lines, sources, confidence, ranges, warnings, payments null, tax_location.resolution), limitations, and routing to siblings. Nothing essential for correct invocation appears missing.

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 13 parameters, including field-level notes like buyer_zip resolving state/county/city. The description adds little parameter-level detail beyond clarifying trade-in handling (negative equity added, balance due after trade), which is mainly output semantics. Baseline 3 is appropriate when the schema does the heavy lifting.

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 states a precise verb and resource: an itemized out-the-door estimate for ONE listing, scoped to the buyer's state, county and city, for the 8 covered states. It enumerates the cost lines it produces and explicitly distinguishes itself from get_price_breakdown (price/fees only) and get_payment_estimate (monthly payment). An agent can route correctly without opening any 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?

It names alternatives and the exact conditions that select them: 'Use get_price_breakdown instead for only the dealer's listed price and fees, and get_payment_estimate to turn this total into a monthly finance payment.' It also tells the agent to read warnings and explains the trade-in case where the total becomes the balance due.

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