Re-run saved Facebook Marketplace watches and report new listings, price drops, and target-price hits since the last check. First run sets a baseline.
Re-run saved watches and report only what changed since each one's last check: new listings, price drops, target-price hits. The first check of a watch sets a baseline.
| Name | Required | Description | Default |
|---|---|---|---|
| name | No | One watch; omit for all. |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only supply openWorldHint=true, so the description carries the behavioral load and does it well: it discloses delta semantics (only changes since last check are reported) and the baseline rule for a watch's first run. It stops short of mentioning auth requirements or rate limits, but the core behavioral contract is unusually clear.
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 tight sentences, front-loaded with the action and the return categories, with the baseline caveat placed last where it belongs. No filler words.
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 usefully enumerates what comes back, which an agent needs. Minor gaps remain around authentication and whether the tool blocks or returns immediately, but for a one-parameter read tool the coverage is strong.
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% and the single 'name' parameter is already documented as 'One watch; omit for all.' The description adds no syntax or naming details beyond the schema, so the baseline 3 applies.
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 ('Re-run') and resource ('saved watches') and enumerates the exact output categories: new listings, price drops, target-price hits. This distinguishes it clearly from sibling marketplace_watch (which creates watches) and marketplace_search (ad-hoc queries).
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 phrase 'saved watches' implies a watch must exist first, and 'omit for all' scopes the operation, but the description never names when to prefer this over marketplace_watch or marketplace_status, nor states prerequisites such as being logged in despite the marketplace_login sibling.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.