opentax

verify_fact

Fact-check a claimed dollar amount about tax law ('the 2026 MFJ standard deduction is $32,200', 'CTC is $2,000 per child') against the corpus. Returns verified / refuted (with the correct value and citation) / unknown. Never states a verdict it cannot ground.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "query": "<query>",
      "claimedAmount": "<claimedAmount>"
    },
    "name": "verify_fact"
  }
}

Input Schema

Name	Required	Description
`asOf`	No
`query`	Yes	what the amount is, e.g. 'standard deduction'
`filingStatus`	No
`claimedAmount`	Yes	dollars, e.g. 50000 or "1234.56"

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 26, 2026
- addedInput schema / properties / query / maxLength
```
Added value: +2000
```
First observedJul 24, 2026

TDQS

B3.4/5.0

Behavior2/5

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

No annotations exist, so the description carries the full disclosure burden. It usefully enumerates the three outcomes (verified / refuted with correct value and citation / unknown) and states an epistemic policy ('never states a verdict it cannot ground'), but says nothing about read-only vs mutating behavior, what the 'corpus' covers or how current it is, or how asOf defaults when omitted.

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?

Three short sentences, front-loaded with the verb and an example, then the return contract. No filler and nothing that could be cut without losing information.

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

Completeness4/5

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

There is no output schema, and the description does the responsible thing by describing the three possible verdicts and the citation returned with a refutation. What remains thin is the parameter story around asOf and the sibling boundary, but for a two-required-param lookup tool this is close to sufficient.

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

Parameters3/5

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

Schema coverage is 50%: query and claimedAmount are documented in the schema, while asOf and filingStatus are bare. The examples implicitly illustrate both ('the 2026 MFJ standard deduction') by pairing a year and a filing status with the claim, which is real added value, but the description never explains these parameters or the default/current-year behavior of asOf.

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

Purpose4/5

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

States a specific verb (fact-check) plus a narrow resource (a claimed dollar amount about tax law), and grounds it with two concrete example claims so the agent knows exactly the shape of input. It does not, however, differentiate itself from the close sibling verify_tax_claim, so the agent cannot tell the two apart from the description alone.

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

Usage Guidelines3/5

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

Usage is implied by the examples (checking a single dollar figure against the corpus), but there is no explicit when-to-use / when-not-to-use guidance and no routing to verify_tax_claim or lookup_tax_parameter for the adjacent cases.

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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