MCP Policies

Control which NexumAPI MCP tools an agent can use.

MCP policies control which SymXchange services and operations are available to an agent. A policy can narrow the services and versions already enabled for an organization's NaaS deployment, but it cannot expose a service or version that the deployment does not allow.

Start with the smallest set of read-only tools your workflow needs. Enable write operations only when the use case requires them.

Request a policy

Email [e-mail] and include:

• The credit union and NaaS environment

• The Sym number and SymXchange version or versions the agent should use

• The services to expose, such as account, findby, poweron, or transactions

• The operations or workflows the agent needs, such as account reads, FindBy searches, PowerOn execution, transaction posting, or user management

• Whether write-capable tools should be enabled

• Any services, operations, or workflows that should be explicitly excluded

The examples below are not request payloads. They show the level of detail that helps us configure and review your policy.

Policy controls

Use allowedServiceVerbs for generic record access:

• get

• list

• search

• create

• update

• delete

Use allowedOperations for specific SymXchange operations used by FindBy, PowerOn, transactions, user management, file workflows, and other curated workflows.

Additional controls can restrict:

• SymXchange versions with allowedVersions

• Credential shapes with allowedCredentialTypes

• Users or applications with allowedIdentities

• All write-capable tools with allowWrites

Optional fields act as wildcards. For example, a service verb without a recordType applies to every record type otherwise allowed by the policy.

Read-only account lookup

This policy permits Account record reads and three FindBy operations:

{
  "mcp": {
    "enabled": true,
    "allowWrites": false,
    "allowedServices": ["account", "findby"],
    "allowedVersions": ["persistent", "2022.01"],
    "allowedServiceVerbs": [
      { "service": "account", "verb": "get", "recordType": "Account" }
    ],
    "allowedOperations": [
      { "service": "findby", "operation": "findByShortName" },
      { "service": "findby", "operation": "findBySSN" },
      { "service": "findby", "operation": "findByMICR" }
    ],
    "allowedCredentialTypes": ["AdministrativeCredentials", "UserNumberCredentials"]
  }
}

Pattern-based record reads

This broader policy permits Account service reads for any record type and either approved version:

{
  "mcp": {
    "enabled": true,
    "allowWrites": false,
    "allowedServices": ["account"],
    "allowedVersions": ["persistent", "2022.01"],
    "allowedServiceVerbs": [
      { "service": "account", "verb": "get" },
      { "service": "account", "verb": "list" },
      { "service": "account", "verb": "search" }
    ]
  }
}

Write-capable policies

Write tools are disabled unless the policy explicitly enables them. Depending on the services allowed, write-capable tools can include:

• create_record

• update_record

• delete_record

• Transaction, PowerOn, user-management, file, batch, balancing, credit-report, and cash-machine tools that change SymXchange data

A write-capable policy should name each required operation:

{
  "mcp": {
    "enabled": true,
    "allowWrites": true,
    "allowedServices": ["poweron", "transactions"],
    "allowedVersions": ["2022.01"],
    "allowedOperations": [
      { "service": "poweron", "operation": "executePowerOn", "version": "2022.01" },
      { "service": "poweron", "operation": "executeMCWPowerOn", "version": "2022.01" },
      { "service": "transactions", "operation": "getDonorRecipientAccounts", "version": "2022.01" },
      { "service": "transactions", "operation": "deposit", "version": "2022.01" },
      { "service": "transactions", "operation": "reverseDeposit", "version": "2022.01" }
    ],
    "allowedCredentialTypes": ["AdministrativeCredentials"],
    "allowedIdentities": ["[e-mail]"]
  }
}

For write workflows, call describe_operation first. Include ProcessorUser with AdministrativeCredentials when SymXchange write attribution is required.

Next steps

• Use the MCP Quickstart to connect a client and make your first read.

• Use Credentials to choose a supported SymXchange credential type.

• Use Capabilities for a broader MCP feature overview.