Track local Facebook Marketplace price history to check if a listing has dropped in price, or find past listings by title to see prior prices.
Local price history recorded by earlier searches: one listing's price changes (by id/URL) or past listings whose title matches some text. Useful for 'has this dropped?' and 'what did these go for last month?'.
| Name | Required | Description | Default |
|---|---|---|---|
| listing | No | ||
| title_contains | No |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnlyHint=true, so safety is covered. The description adds the genuinely non-obvious behavioral fact that results come from locally recorded earlier searches, implying coverage depends on prior activity and may be empty. It does not say what happens when no history exists.
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, zero filler, with the source-of-data caveat front-loaded before the two retrieval modes. Every clause earns its place.
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 read-only, no-output-schema tool the description need not explain return values, and it covers both modes adequately. But it leaves open the interaction between the two optional parameters and the empty-history case, which an agent would need to call it confidently.
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?
With 0% schema description coverage, the description must carry the load: it does map 'listing' to a single listing by id/URL and 'title_contains' to title text matching. However, it omits the format of the id/URL, and since both parameters are optional it never explains precedence or what happens when both (or neither) are supplied.
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 resource (local price history) and the two retrieval modes (single listing's price changes by id/URL, or past listings matching a title). The phrase 'recorded by earlier searches' distinguishes it from live-lookup siblings like marketplace_search and marketplace_listing, though no sibling is named explicitly.
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?
Gives concrete trigger questions ('has this dropped?', 'what did these go for last month?') that map directly to the two parameter modes, so an agent can tell when to call it. It stops short of stating when NOT to use it or which sibling to prefer for live data.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.