Claim Grounding

by io.github.truepointmarketingpartners-dotcom

Verify claim

verify_claim

Read-onlyIdempotent

Check one factual claim against public Wikipedia sources and return a verdict (supported, contradicted, outdated, mixed or insufficient_evidence), a confidence score, a short reason, the supporting quote and the source URL. Says insufficient_evidence instead of guessing. Price: $1.00 USDC on Base per call via x402; this MCP call returns payment instructions and the paid HTTP route POST /v1/verify_claim returns the verdict. For a multi-source check use deep_verify. Read-only.

Input Schema

Name	Required	Description
`claim`	Yes	One factual sentence to check.
`sources`	No	Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type "caller". The response lists what was used in sources_used.
`sources_only`	No	Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array.

Output Schema

Name	Required	Description
`tool`	Yes	Tool name.
`result`	No	Paid result: { mode, claim: { text, verdict, confidence, rationale_short, citations[] }, why, source, receipt }.
`status`	Yes	payment_required: pay the HTTP route with x402 to get the result. ok: result is included.
`message`	Yes	Human-readable summary.
`payment`	No	Payment instructions. MCP tools/call does not charge or run the paid work; call the HTTP route with x402.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 20, 2026

addedOutput schema / properties / result / properties / claim / properties / next_step

Added value: +{
+  "description": "1.4.8: present only on unsure, low-confidence or unverified high-worthiness claims. A ready-to-send Deep verify request for this claim (optional, paid separately).",
+  "properties": {
+    "body": {
+      "properties": {
+        "claim": {
+          "properties": {
+            "text": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "text"
+          ],
+          "type": "object"
+        }
+      },
+      "required": [
+        "claim"
+      ],
+      "type": "object"
+    },
+    "endpoint": {
+      "format": "uri",
+      "type": "string"
+    },
+    "method": {
+      "const": "POST",
+      "type": "string"
+    },
+    "price_usd": {
+      "type": "number"
+    },
+    "tool": {
+      "const": "deep_verify",
+      "type": "string"
+    },
+    "why": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "tool",
+    "why",
+    "price_usd",
+    "endpoint",
+    "method",
+    "body"
+  ],
+  "type": "object"
+}

Changed4 schema fields changedOct 13, 2026

addedInput schema / properties / sources

Added value: +{
+  "description": "Optional. Up to 10 sources of your own, used as extra evidence next to the public sources and cited with provider and source_type \"caller\". The response lists what was used in sources_used.",
+  "items": {
+    "additionalProperties": false,
+    "anyOf": [
+      {
+        "required": [
+          "url"
+        ]
+      },
+      {
+        "required": [
+          "text"
+        ]
+      }
+    ],
+    "description": "One source: {url} for a public https page we fetch, or {text, title?, url?} for text you already have.",
+    "properties": {
+      "text": {
+        "description": "Source text to check the claim against (up to 20,000 characters). When given, no fetch is made.",
+        "maxLength": 20000,
+        "minLength": 1,
+        "type": "string"
+      },
+      "title": {
+        "description": "Optional title shown in citations.",
+        "maxLength": 200,
+        "type": "string"
+      },
+      "url": {
+        "description": "Public https URL. Fetched with a 3.5 s timeout and a 512 KB cap; http, file and other schemes, private / loopback / link-local / metadata addresses, IP-literal hosts, custom ports and URLs with credentials are rejected (HTTP 400, not charged). With text, it is only the citation link.",
+        "format": "uri",
+        "maxLength": 2048,
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "maxItems": 10,
+  "type": "array"
+}

addedInput schema / properties / sources_only

Added value: +{
+  "default": false,
+  "description": "Optional. true = judge the claim only against your sources (no public-source lookups). Needs a non-empty sources array.",
+  "type": "boolean"
+}

addedOutput schema / properties / result / properties / claim / properties / citations / description

Added value: +"Evidence quotes with url, title and source_type (wikipedia, wikidata, news, europepmc, fred, sec_edgar, or caller for your own sources)."

addedOutput schema / properties / result / properties / sources_used

Added value: +{
+  "description": "Present when you sent sources: one entry per source with index, kind, url, title, status (used, fetch_failed, empty), chars and reason.",
+  "items": {
+    "type": "object"
+  },
+  "type": "array"
+}

First observedOct 12, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already cover read-only/idempotent/open-world, but the description adds material context beyond them: the $1.00 USDC-on-Base x402 price, the two-step flow (this MCP call returns payment instructions, the paid HTTP route POST /v1/verify_claim returns the verdict), and the fallback behavior of returning insufficient_evidence rather than guessing.

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-loads the core action and its return values in the first sentence, then appends payment/route mechanics and sibling routing. Dense but every clause is load-bearing; the payment sentence is slightly tangled and could be split, keeping it short of a 5.

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?

With an output schema present, return values need not be detailed, yet the description still names the verdict set and the evidence fields. Combined with cost/route disclosure and source-handling semantics, an agent has everything needed to invoke it correctly.

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 100%, so the baseline is 3, but the description adds value on how caller-supplied sources are treated: they are extra evidence alongside public sources, cited with provider and source_type "caller", and listed back in sources_used. It does not itself explain the url/text/title source shapes, which the schema handles.

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+resource ('Check one factual claim against public Wikipedia sources') and enumerates the exact verdict values returned. It also names the sibling it is not: multi-source work belongs to deep_verify, so the agent can distinguish single-claim scope without opening the schema.

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

Usage Guidelines4/5

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

Gives explicit routing to deep_verify for multi-source checks and clarifies the sources_only condition (judge only against caller sources). It does not address when to prefer check_answer or extract_claims, and the 'use when' framing is implied by the singular-claim constraint rather than stated.

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

All Claim Grounding tools Inspect

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