RedTape: Spain, Mexico & Colombia business data

Mexico SAT 69-B (EFOS) lookup by RFC

mx_sat_69b_lookup

Read-only

Look up one Mexican RFC in the SAT 69-B complete list (taxpayers presumed to invoice non-existent operations, EFOS). Returns whether it is listed and its situation (Presunto, Desvirtuado, Definitivo, Sentencia Favorable) with oficio numbers, publication dates, the data cut-off and the source citation. Lookup by RFC only; persona física names are never returned. Source: SAT open data (Libre Uso MX); not an official SAT service. Free: 20 calls per client per UTC day, shared by the Mexico tools (mx_sat_69b_lookup, mx_rfc_validate). When the free quota is used up the tool returns an error naming the paid HTTP endpoint https://mx.redtapeapi.com/v1/mx/sat/69b ($0.005 USDC per successful call over x402 on Base, no account or API key).

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": {
      "rfc": "<rfc>"
    },
    "name": "mx_sat_69b_lookup"
  }
}

Input Schema

Name	Required	Description	Default
`rfc`	Yes	Mexican RFC, 12 (persona moral) or 13 (persona física) characters

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 7, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Goes well beyond readOnlyHint/openWorldHint: it enumerates the possible situation values (Presunto, Desvirtuado, Definitivo, Sentencia Favorable), the fields returned (oficio numbers, publication dates, cut-off, citation), the 20-calls-per-UTC-day shared quota, and the exact error behavior with the paid fallback endpoint and price. This is unusually complete operational disclosure.

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?

Core purpose and return shape come first, then the quota/pricing caveat, which is front-loaded enough to be actionable. The pricing and x402 details are lengthy, but they justify their space because they explain how to proceed after quota exhaustion.

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 no output schema, the description carries the return-value burden and does so by listing the situation values and accompanying fields. Source attribution, quota, and failure behavior round out everything an agent needs to invoke it correctly.

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 100% and the single 'rfc' parameter is already documented as 12 or 13 characters, so the schema does the heavy lifting. The description adds only that lookups are RFC-keyed and that persona física names are never returned, which is useful context but not parameter-level syntax guidance beyond the schema.

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 ('Look up one Mexican RFC in the SAT 69-B complete list') and immediately glosses what 69-B/EFOS means, so an agent understands the domain without prior knowledge. It is clearly distinguishable from mx_rfc_validate, which is named only as a quota sharer rather than a functional duplicate.

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 clear conditions: RFC-only lookup, persona física names never returned, and disclosure that the tool is not an official SAT service. It does not, however, state explicitly when an agent should prefer mx_rfc_validate over this tool, leaving the sibling routing to inference.

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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