fraud-mcp

Evaluate fraud rules (deterministic)

evaluate_fraud_rules

Read-onlyIdempotent

Run all seven fraud rules against an account to determine which ones fire and why, returning evidence, thresholds, and a deterministic risk verdict for fraud investigation.

Instructions

Run all seven fraud rules against an account and return which ones fired, and why.

THIS IS THE AUTHORITATIVE RISK VERDICT. The engine is deterministic: the same
account always yields the same result. Do not second-guess it, re-derive it
from raw transactions, or soften it.

Rules evaluated: VELOCITY_BURST, AMOUNT_SPIKE, NEW_GEO_HIGH_VALUE, STRUCTURING,
SHARED_DEVICE, IMPOSSIBLE_TRAVEL, DORMANT_REACTIVATION.

Covers, in plain terms: transaction velocity and card testing, spending
anomalies against the account's own baseline, unfamiliar geography, money
laundering by structuring or smurfing below a reporting threshold, account
takeover and credential stuffing via shared devices, and cloned cards
(impossible travel). Use this tool for ANY question about whether an account
is risky, compromised, laundering, or worth escalating - not only questions
phrased around velocity.

Every rule returns one of three states, and the difference matters:
  FIRED     - the threshold was met; `evidence_txn_ids` lists the transactions.
  NOT_FIRED - evaluated, threshold not met. This is a genuine pass.
  SKIPPED   - could NOT be evaluated (e.g. too little history for a baseline).
              This is an UNKNOWN, not a pass. Report skipped rules explicitly.

Each result carries the thresholds that were applied and the observations
measured against them, so any verdict can be recomputed by hand later. Cite
`rule_id` and `evidence_txn_ids` in anything you write.

Call this BEFORE flag_case. Takes no time window: each rule applies its own
documented lookback.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`account_id`	Yes	Account identifier in the exact form 'ACC-####' (e.g. 'ACC-1013'). Copy it from a previous tool response or the user's message; do not invent or reformat it.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 14, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond the read-only/idempotent annotations, it discloses determinism, the meaningful distinction between FIRED/NOT_FIRED/SKIPPED, and that SKIPPED is an UNKNOWN rather than a pass. It adds that thresholds and observations are returned for manual recomputation, which is behavior an agent needs to trust and report correctly.

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?

Though longer than typical descriptions, it is modular: purpose/authority, rule list, human-readable coverage, ternary result semantics, evidence recomputation, and ordering. Each section earns its place, and the critical directive is front-loaded.

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 rule-evaluation tool with an output schema, it covers the full decision context: all seven rule IDs, what each covers in plain terms, the three result states and their interpretation, evidence/instructions for citing rule_id and evidence_txn_ids, and the relationship to flag_case. Nothing needed to invoke it correctly is left unresolved.

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?

There is one parameter and the schema already documents it thoroughly with format, pattern, examples, and the instruction to copy rather than invent or reformat the account_id. The tool description adds no extra parameter-level meaning, so the baseline of 3 applies.

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 first sentence names a specific verb ('Run all seven fraud rules against an account') and the exact resource ('an account'), then states the return value ('which ones fired, and why'). It differentiates itself from siblings by framing itself as the authoritative risk verdict, so an agent won't confuse it with get_transactions or flag_case.

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?

The description explicitly says to use it for ANY risk-related question, not just ones phrased around velocity, and it gives sequencing advice ('Call this BEFORE flag_case'). It also tells the agent not to second-guess or re-derive from raw transactions. It explains that no time-window parameter is needed because each rule has its own documented lookback.

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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