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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful operational context beyond annotations by stating 'Pricing: 1 credit per call.' It does not cover auth needs, rate limits, or pagination behavior, so it is not fully exhaustive.

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 two sentences and front-loads the core purpose before the pricing note. Every sentence adds value: the first states what it searches and which filters exist, and the second gives cost 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 rich annotations, full schema coverage, and an output schema, the description does not need to explain return values or parameter formats. It covers the core action and cost, but it omits routing guidance relative to nearby marketplace siblings. That gap is not fatal, but it keeps the definition from being fully complete.

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 each of the 13 parameters is already documented in the input schema. The description lists broad filter categories but adds no syntax, format, or boundary details beyond what the schema provides. This matches the baseline of 3 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 specific verb and resource: 'Search Facebook Marketplace items.' It also names the filter dimensions, making the tool's scope clear. However, it does not distinguish this general marketplace search from sibling tools like facebook_marketplace_vehicles, facebook_marketplace_rentals, or facebook_marketplace_listing.

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 implies usage by naming the searchable filters and stating the credit cost. It does not say when to choose this tool over sibling marketplace or general search tools, nor does it list any exclusions or prerequisites.

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