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

Annotations already establish readOnly, idempotent, non-destructive behavior, so the bar is lower. The description adds the meaningful constraint 'Does not invent prices' (no fabricated pricing), which is genuinely useful behavioral context not derivable from the schema or 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?

Three short sentences, front-loaded with the trigger and the return contents. The final 'Does not invent prices' line is slightly tangential to conciseness but carries real behavioral information.

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?

With no output schema, the description carries the burden of describing returns and does so by enumerating the offer types returned. Coverage of what is returned plus the no-invented-prices caveat makes it largely complete for a single-parameter read tool.

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% for the single 'zip' parameter, so the schema already documents the '5-digit US ZIP code' format. The description only restates that ZIP scoping applies, adding no syntax or edge-case detail beyond the schema; baseline 3 is appropriate.

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?

State a specific verb ('Returns') and resource ('Sale offer'), scoped to selling containers to a ZIP. It is clearly distinguishable from the sibling get_rental_offers and enumerates the offer categories (WWT, CWO, One Trip) so an agent knows exactly what comes back.

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?

Explicitly states the trigger: 'Use this when the user asks what containers WCS can sell to a ZIP,' plus a guardrail not to omit One Trip for used/storage queries. It does not name the sibling alternatives (find_market, get_rental_offers) or state when not to use it, so it falls short of a 5.

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