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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint. The description adds error behavior ('unknown returns unit_not_found'), pricing caveats (fees/tax excluded, total estimates), and mandatory agent actions ('Always relay pricing_disclosure'). No contradiction with annotations.

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?

Four dense sentences front-load the purpose and return structure, then address error, pricing, and agent instructions. Every sentence adds value, though a bulleted layout for pricing rules could improve scanability.

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?

Given no output schema, the description covers return shape (photos, options, plain-text description), pricing fields (pricing_disclosure, pricing_coverage), error case, and presentation instructions. It omits potential field variants or rate limits, but is sufficient for correct invocation.

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 0%, but the description fully explains both parameters: identity is a VIN and rooftop_slug comes from network_search results. This adds critical meaning beyond schema length constraints.

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 'Fetch one available unit by identity (VIN) from a named rooftop', specifying the verb, resource, and key identifiers. It distinguishes from siblings like network_search (listing) and inventory_stats (aggregates) by focusing on a single vehicle detail retrieval.

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 explains when to use this tool (fetch a specific vehicle after network_search), how to interpret results (embed photos, handle partial estimates), and references quote_preview for total pricing. It lacks explicit when-not-to-use alternatives beyond the implied sibling distinctions.

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