[FEATURE]: Tool call anomaly detection plugin

[anujshrivastava15]

🧭 Type of Feature

• New feature or capability

🧭 Epic

Title: Tool Call Anomaly Detection Plugin
Goal: Detect unusual tool-calling patterns per user/agent by learning behavioral baselines.
Why now: ContextForge has strong permission-based controls (RBAC, PDP) and content-based security (PII filter, secrets detection), but no way to flag when a user's tool-calling behavior changes — e.g. sudden access to new tools, burst patterns, or off-hours activity. This would complement existing security and feed data into the planned Security Posture Dashboard (#2309).

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🧑🏻‍💻 User Story 1

As a: platform administrator
I want: automatic detection when a user/agent's tool-calling pattern deviates from their baseline
So that: I'm alerted to potentially compromised credentials or prompt injection — even when RBAC permits the access.

✅ Acceptance Criteria

Scenario: Known tool call scores low risk
  Given user "alice" regularly calls "db_query"
  When "alice" calls "db_query" with typical arguments
  Then the plugin allows the call with risk_score < 0.5

Scenario: Novel tool triggers elevated risk
  Given user "alice" has never called "delete_records"
  When "alice" calls "delete_records"
  Then risk_score is elevated and a warning is logged

Scenario: Burst pattern detected
  Given burst_threshold is 20 calls per 60 seconds
  When a user makes 25 calls in 30 seconds
  Then burst score exceeds threshold

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📐 Design Sketch

flowchart TD
    A[Tool Call] --> B{Learning phase?}
    B -->|Yes| C[Record baseline, allow]
    B -->|No| D[Score: novelty + burst + frequency + off-hours]
    D --> E{Above threshold?}
    E -->|Block mode| F[Block + violation]
    E -->|Warn mode| G[Allow + warn log]
    E -->|Below| H[Allow + metadata]

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• Hooks: tool_pre_invoke, tool_post_invoke
• Dependencies: None — pure Python, in-memory baselines
• Priority: Runs after RBAC/PDP checks

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🔗 MCP Standards Check

• Change adheres to current MCP specifications
• No breaking changes to existing MCP-compliant integrations

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🔄 Alternatives Considered

None at this stage.

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📓 Additional Context

None.