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

The annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is fully covered by structured data. The description adds nothing beyond that: no note on whether a missing/private listing errors, no rate-limit or auth context, no indication of what 'detailed info' includes. It essentially restates the read-only nature the annotations already convey.

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?

A single short sentence with zero filler and the resource front-loaded. Appropriately sized for a one-parameter getter, though its brevity leaves the gaps in usage and behavior unfilled rather than being maximally efficient.

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?

An output schema exists, so return values need not be described, and annotations cover safety. What's missing is disambiguation from the many other facebook_marketplace_* siblings and any note on failure behavior for an invalid/removed listing. Adequate but with clear gaps for a tool in a dense sibling cluster.

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?

One required parameter (listing_id) with 100% schema description coverage, so the schema already carries the semantics. The description adds no format or sourcing detail (e.g., where a listing_id comes from, whether it comes from a search result). Baseline 3 applies 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?

States a specific verb (Get) and resource (a single Marketplace listing) with the 'detail for one item' scope that separates it from the marketplace search/listing-collection siblings. However, it never names those siblings (facebook_marketplace_search, facebook_marketplace_seller), so the differentiation must be inferred from the phrase 'a single'.

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?

No when-to-use guidance and no alternatives named, despite ~5 marketplace siblings (search, seller, categories, rentals, vehicles) that could plausibly be confused with this one. An agent gets no explicit routing rule for picking this tool over facebook_marketplace_search or facebook_marketplace_seller.

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