apis-io

watch_listing

Idempotent

INFLUENCE — be told when a listing you care about moves: score changes, band changes, agent-band changes, or a check closing. REQUIRES a destination: contact (an email address), callback_url (an https endpoint that receives signed JSON), or both. The first pass after registering records where the provider stands and sends nothing, so the first notification you get is about a real move. agent_band is the one worth having — it carries the gate that caused the change, which a provider cannot compute about themselves. Re-registering the same slug REPLACES its event set rather than adding a second watch. list_watches shows what you hold; unwatch_listing removes one. Priced B1 (single-entity synthesis) — $0.01 per call under pay-as-you-go; included in Understanding and Influence. See apis://prices.

Input Schema

TableJSON Schema

Name	Required	Description
`slug`	Yes
`events`	No	score, band, agent_band, check. Defaults to all four.
`contact`	No	Email address for notifications.
`context`	No	Optional: why you are asking. One sentence — the task you are trying to complete, or what you expect to get back. Never included in the answer and never used to rank; it is read only when a result turns out to be wrong, which is when knowing the intent is what makes the report actionable.
`callback_url`	No	HTTPS endpoint for signed webhook delivery.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 12, 2026

addedInput schema / properties / callback_url

Added value: +{
+  "description": "HTTPS endpoint for signed webhook delivery.",
+  "type": "string"
+}

addedInput schema / properties / contact

Added value: +{
+  "description": "Email address for notifications.",
+  "type": "string"
+}

changedInput schema / properties / events / description

Previous value: -"score, band, check. Defaults to all three."New value: +"score, band, agent_band, check. Defaults to all four."

AddedSep 2, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations provide only basic flags (readOnlyHint=false, idempotentHint=true, destructiveHint=false). The description adds substantial behavioral detail: the first pass records state and sends nothing, re-registering replaces the event set, and it notes the pricing tier. This goes well beyond what annotations convey and sets correct expectations for a watch operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single dense paragraph but every sentence earns its place: purpose, requirement, behavioral nuance, a strategic tip, management alternatives, and pricing. It is front-loaded with the core purpose and remains focused, not padded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a write operation with 5 parameters and no output schema, the description covers everything an agent needs: what events exist, how to configure destinations, the initial no-op behavior, re-registration semantics, how to manage watches, and pricing. No critical gaps remain for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 80% (4 of 5 parameters have descriptions), so the baseline is 3. The description enriches this by explaining the destination requirement (contact/callback_url or both), the meaning of the agent_band event (carries the gate that caused the change), and the effect of re-registering a slug on the events parameter. It adds value beyond the schema without repeating it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a clear verb and resource: 'be told when a listing you care about moves', enumerating the exact event types (score, band, agent_band, check closing). It distinguishes itself from sibling tools like list_watches and unwatch_listing, making its purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly states when to use the tool (to be notified of listing moves) and names alternatives: 'list_watches shows what you hold; unwatch_listing removes one.' It also gives guidance on choosing events ('agent_band is the one worth having') and clarifies the destination requirement, so an agent knows exactly when to pick this over related tools.

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

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