uml-diagram

UML & Diagram Generation via Kroki

MCP Server

Tools

generate_uml

Generate a diagram and optionally save to disk.

Returns: { code, url, playground, local_path, content_base64, error }

generate_diagram_url

Get the Kroki rendering URL and optional base64 content without saving to disk.

Returns: { code, url, playground, content_base64, error }

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Supported Diagram Types (27+)

PlantUML-based

Network & Infrastructure

Other Backends

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Network Engineering Examples

Network Topology (nwdiag)

generate_uml(
  diagram_type="nwdiag",
  code="""
nwdiag {
  network dmz {
    address = "210.x.x.x/24"
    web01 [address = "210.x.x.1"];
    web02 [address = "210.x.x.2"];
  }
  network internal {
    address = "172.x.x.x/24"
    web01 [address = "172.x.x.1"];
    web02 [address = "172.x.x.2"];
    db01;
  }
}
""",
  output_format="svg"
)

Rack Diagram (rackdiag)

generate_uml(
  diagram_type="rackdiag",
  code="""
rackdiag {
  16U;
  1: UPS;
  2: UPS;
  3: Patch Panel;
  4: Catalyst 9300;
  5: Catalyst 9300;
  6: Nexus 9000;
  7: Nexus 9000;
  8: ASR 1001-X;
  9: ASR 1001-X;
  10: BIG-IP i5800;
  11: BIG-IP i5800;
  12: UCS C220;
  13: UCS C220;
  14: UCS C220;
  15: UCS C220;
  16: Cable Management;
}
""",
  output_format="png"
)

Packet Header (packetdiag)

generate_uml(
  diagram_type="packetdiag",
  code="""
packetdiag {
  colwidth = 32
  node_height = 72
  0-3: Version
  4-7: IHL
  8-15: DSCP / ECN
  16-31: Total Length
  32-47: Identification
  48-50: Flags
  51-63: Fragment Offset
  64-71: TTL
  72-79: Protocol
  80-95: Header Checksum
  96-127: Source Address
  128-159: Destination Address
}
""",
  output_format="svg"
)

BGP State Machine (state)

generate_uml(
  diagram_type="state",
  code="""
@startuml
[*] --> Idle
Idle --> Connect : Start
Connect --> OpenSent : TCP established
Connect --> Active : TCP failed
Active --> OpenSent : TCP established
Active --> Connect : ConnectRetry timer
OpenSent --> OpenConfirm : OPEN received (valid)
OpenSent --> Idle : OPEN received (error)
OpenConfirm --> Established : KEEPALIVE received
OpenConfirm --> Idle : Hold timer expired
Established --> Idle : NOTIFICATION / Hold expired
Established : Process UPDATE messages
@enduml
""",
  output_format="svg"
)

OSPF Area Design (class)

generate_uml(
  diagram_type="class",
  code="""
@startuml
package "Area 0 - Backbone" {
  class "Core-1" as C1 { router-id: 1.1.1.1 }
  class "Core-2" as C2 { router-id: 2.2.2.2 }
  C1 -- C2 : 10G P2P
}
package "Area 1 - Campus" {
  class "Dist-1" as D1 { router-id: 3.3.3.3 }
  class "Dist-2" as D2 { router-id: 4.4.4.4 }
}
package "Area 2 - DC" {
  class "Spine-1" as S1 { router-id: 5.5.5.5 }
  class "Spine-2" as S2 { router-id: 6.6.6.6 }
}
C1 -- D1 : ABR
C2 -- D2 : ABR
C1 -- S1 : ABR
C2 -- S2 : ABR
@enduml
""",
  output_format="svg"
)

Sequence: Change Request Flow

generate_uml(
  diagram_type="sequence",
  code="""
@startuml
actor Engineer
participant NetClaw
participant ServiceNow
participant Device
participant GAIT

Engineer -> NetClaw : "Add Loopback99"
NetClaw -> ServiceNow : Create Change Request
ServiceNow --> NetClaw : CR-12345 (New)
NetClaw -> ServiceNow : Wait for approval
ServiceNow --> NetClaw : CR-12345 (Implement)
NetClaw -> Device : Capture baseline
Device --> NetClaw : Running config
NetClaw -> Device : Apply config
Device --> NetClaw : Config applied
NetClaw -> Device : Verify change
Device --> NetClaw : Loopback99 up/up
NetClaw -> ServiceNow : Close CR-12345
NetClaw -> GAIT : Record full audit trail
NetClaw --> Engineer : Done. Verified.
@enduml
""",
  output_format="svg"
)

C4 Architecture (structurizr)

generate_uml(
  diagram_type="structurizr",
  code="""
workspace {
  model {
    engineer = person "Network Engineer"
    netclaw = softwareSystem "NetClaw" {
      openclaw = container "OpenClaw Agent"
      pyats = container "pyATS MCP"
      gait = container "GAIT MCP"
    }
    network = softwareSystem "Network Devices"
    servicenow = softwareSystem "ServiceNow"

    engineer -> openclaw "Chat"
    openclaw -> pyats "MCP (stdio)"
    openclaw -> gait "MCP (stdio)"
    pyats -> network "SSH/NETCONF"
    openclaw -> servicenow "REST API"
  }
  views {
    container netclaw {
      include *
      autoLayout
    }
  }
}
""",
  output_format="svg"
)

---

Workflows

1. Network Topology Documentation

pyats-topology → CDP/LLDP discovery data
→ generate_uml(type="nwdiag") → network topology diagram
→ msgraph-files → upload to SharePoint
→ GAIT

2. Protocol State Machine Reference

generate_uml(type="state") → BGP/OSPF/STP state machine
→ Share in Slack/Teams for team reference
→ GAIT

3. Change Request Visualization

servicenow-change-workflow → CR details
→ generate_uml(type="sequence") → change flow diagram
→ Attach to ServiceNow CR or GAIT log
→ GAIT

4. Data Center Rack Documentation

generate_uml(type="rackdiag") → rack layout
→ generate_uml(type="nwdiag") → network connections
→ Cross-reference with NetBox rack/device data
→ msgraph-files → upload to SharePoint
→ GAIT

5. Packet Format Reference

generate_uml(type="packetdiag") → protocol header diagram
→ rfc-lookup → verify against RFC
→ Share as reference material
→ GAIT

6. Architecture Documentation

generate_uml(type="structurizr" or "c4plantuml") → C4 architecture views
→ generate_uml(type="deployment") → deployment diagram
→ generate_uml(type="component") → component breakdown
→ msgraph-files → upload to SharePoint
→ GAIT

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Integration with Other Skills

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Comparison: UML MCP vs Draw.io vs Markmap

When to use UML MCP:

• Protocol state machines (BGP FSM, OSPF states, STP states)
• Network topology diagrams from code (nwdiag)
• Rack layouts (rackdiag)
• Packet header documentation (packetdiag)
• Sequence diagrams (change workflows, protocol exchanges)
• Architecture documentation (C4, component, deployment)
• Database schema diagrams (ERD, DBML)
• Any diagram type supported by Kroki

When to use Draw.io:

• Interactive topology editing
• Native .drawio files for team collaboration
• Color-coded reconciliation status overlays

When to use Markmap:

• Hierarchical data (OSPF areas, BGP peers, config structure)
• Quick visual summaries from markdown

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Guardrails

• All operations are read-only — generates diagrams, never modifies network state
• Public Kroki by default — diagram source code is sent to kroki.io for rendering; use a local Kroki instance (KROKI_SERVER) for sensitive topology data
• No secrets in diagrams — never include IP credentials, passwords, or SNMP communities in diagram source code
• Record in GAIT — every diagram generation must be logged