facebook_marketplace_item

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

With no annotations, the description carries the full burden of behavioral disclosure. It explicitly explains that Facebook's logged-out payload withholds seller identity, so the response has no seller field by design. The phrase 'logged-out payload' also signals an unauthenticated public read, providing meaningful behavioral context.

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?

Two sentences, front-loaded with the main action, then the necessary return fields and a single justification for the missing seller field. Every sentence earns its place with zero redundancy.

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 one-parameter fetch, the description lists all expected return fields and explains the one notable omission (seller identity). With no output schema present, this return-value disclosure is essential and sufficiently complete for a tool of this simplicity.

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 schema already documents id as 'Facebook Marketplace numeric listing id' with 100% coverage. The description repeats the numeric id expectation but adds no new details such as format, length, examples, or validation constraints, so it does not add meaningful value beyond the schema.

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 opens with 'Get Facebook Marketplace listing' and specifies it fetches public data for a single listing given a numeric id. It enumerates the returned fields (title, price, description, condition, photo, location), clearly differentiating it from facebook_marketplace_search and other sibling item tools.

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 clearly states the precondition of having a numeric listing id, which implies the user must first obtain an id, likely via a search tool. However, it does not explicitly name facebook_marketplace_search as the alternative for finding ids, so the guidance is clear but lacks an explicit exclusion/alternative statement.

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