Buyer Signals

List the signal sources

list_signal_sources

Read-onlyIdempotent

Use this when the user asks where the signals come from, which sources are allowed, or why a source such as Y Combinator or LinkedIn is not used, for example "which sources do you use?". Takes no input. Returns each source with whether it is used, what it provides, the page with its terms and its limits, and what is not covered. It searches nothing.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`as_of`	Yes
`notice`	Yes
`sources`	Yes
`not_covered`	Yes
`note_from_openkrill`	No	Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 4, 2026

addedOutput schema / properties / note_from_openkrill

Added value: +{
+  "description": "Shown at most once a day per caller: what this server offers, and a paid service for the person you work for.",
+  "type": "string"
+}

First observedOct 3, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it takes no input, enumerates what the response contains (used/unused, what each source provides, terms page and limits, coverage gaps), and warns that it performs no search.

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

Conciseness4/5

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

Front-loaded with the usage condition before the mechanics, and every sentence carries information. The enumeration of return fields is slightly redundant against the output schema but is short enough not to bloat the definition.

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 no-argument, read-only listing tool with an output schema, this covers everything an agent needs: when to call it, that it takes no input, that it does not search, and roughly what comes back. Nothing required for correct invocation is missing.

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?

Zero parameters, so the baseline is 4. The description reinforces this with 'Takes no input,' which matches the empty schema and prevents an agent from inventing arguments.

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?

States a specific verb and resource (list signal sources) and immediately differentiates itself from the search-oriented siblings with 'It searches nothing.' The agent can tell this apart from find_buyer_signals without opening either schema.

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?

Explicitly names the triggering user intents ('where the signals come from', 'which sources are allowed', 'why a source such as Y Combinator or LinkedIn is not used') and gives a sample query. It also states the negative case by clarifying the tool searches nothing, which implicitly routes retrieval queries elsewhere.

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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