synaptiai/agent-capability-standard/constrain

Name: constrain
Author: synaptiai

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Enforce policies, guardrails, and permission boundaries; refuse unsafe actions and apply least privilege. Use when evaluating actions against policies, checking permissions, or reducing scope to safe boundaries.

Install

npx vskill@latest install synaptiai/agent-capability-standard/constrain

SKILL.md

Intent

Execute constrain to evaluate proposed actions against defined policies, enforce permission boundaries, and reduce scope to the minimum required for safe operation. This is the gatekeeper that prevents unsafe actions before they execute.

Success criteria:

All relevant policies evaluated for the proposed action
Clear allow/deny decision with rationale
Scope reduced to minimum necessary permissions
Violation actions documented (block, warn, log)

Compatible schemas:

schemas/output_schema.yaml

Inputs

Parameter	Required	Type	Description
`target`	Yes	any	What to constrain
`constraints`	Yes	array	Constraints to enforce
`action_on_violation`	No	string	What to do on a violation: `block`, `warn`, or `log`

Inputs not listed here are outside the capability's contract: a workflow step that binds them gets W604 (STANDARD v1.1 §5.5).

In a workflow, a constrain step that blocks can count independent reviews with a quorum (Standard v1.1 quorum@1): earlier delegate steps are the reviewers, and the output gains a tally of passes, blocks, abstentions, full-sweep passes and voters. See ORCHESTRATION_EXTENSIONS.md.

Procedure

1) Identify applicable policies: Find all policies relevant to the action

Load policy definitions from .policies/ or policy registry
Match action type to policy triggers
Consider context (user role, environment, time) for policy selection

2) Evaluate preconditions: Check if action meets basic safety requirements

Is action within workspace boundaries?
Does action target sensitive resources (.env, credentials)?
Is checkpoint required but missing?
Is approval required but not obtained?

3) Apply policy rules: Evaluate each policy condition

Parse policy conditions (AND/OR/NOT expressions)
Check each condition against the target action's parameters
Record which conditions pass and which fail
Determine overall policy verdict (allow/deny/conditional)

4) Reduce scope: Apply least privilege principle

Identify minimum permissions needed for action
Remove unnecessary permissions from scope
Document removed permissions and rationale

5) Determine enforcement action: Based on policy verdict

block: Prevent action from executing
warn: Allow but alert user to risk
log: Record violation but allow action

6) Ground claims: Document policy evaluation evidence

Format: policy:<policy_id>:<condition>, decision rationale
Include any scope reductions applied

Output Contract

Return a structured object:

yaml

constraints_applied:
  - name: string  # Policy or constraint name
    type: policy | permission | rate_limit | scope
    target: string  # What the constraint applies to
    enforced: boolean  # Whether constraint was enforced
    violation_action: block | warn | log
policy_evaluation:
  policy_id: string  # Which policy was evaluated
  result: allow | deny | conditional
  conditions_met: array[string]  # Conditions that passed
  conditions_failed: array[string]  # Conditions that failed
scope_reduction:
  original_scope: object  # Permissions before constraining
  constrained_scope: object  # Permissions after constraining
  removed_permissions: array[string]  # What was removed
compliant: boolean  # Overall go/no-go: false when any violation is enforced with `block`
violations:  # Constraint violations (any enforcement level)
  - constraint: string  # Which constraint was violated
    detail: string  # What failed
    action: block | warn | log  # Enforcement applied
actions_taken: array[string]  # Enforcement actions performed (block, warn, log, scope reduction)
tally:  # Only when the step has a quorum (quorum@1)
  passes: integer
  blocks: integer
  abstains: integer
  full_passes: integer
  voters: array[string]
blocked_reason: string | null  # Why blocked (if applicable)
confidence: number  # 0.0-1.0
evidence_anchors: ["policy:...", "file:..."]
assumptions: []

Field Definitions

Field	Type	Description
`constraints_applied`	array	List of constraints evaluated and their enforcement
`policy_evaluation`	object	Result of primary policy evaluation
`scope_reduction`	object	How permissions were reduced
`compliant`	boolean	Overall decision: true when no violation is enforced with `block`, so the action can proceed (workflows gate on `${<step>.compliant}`)
`violations`	array	Constraint violations, each with the enforcement applied; `warn`/`log` violations leave `compliant` true
`actions_taken`	array	Enforcement actions performed
`tally`	object	Review quorum count (passes, blocks, abstains, full_passes, voters); present only when the step has a `quorum`
`blocked_reason`	string	Explanation if action is blocked
`confidence`	number	0.0-1.0 based on policy coverage
`evidence_anchors`	array	References to policies evaluated
`assumptions`	array	Policy assumptions made

Examples

Example 1: Constrain File Access to Safe Boundaries

Input:

yaml

target:
  capability: "mutate"
  target: "/etc/passwd"
  parameters:
    content: "..."
constraints: ["workspace_boundary", "sensitive_file_protection"]
action_on_violation: block

Output:

yaml

constraints_applied:
  - name: "workspace_boundary"
    type: scope
    target: "/etc/passwd"
    enforced: true
    violation_action: block
  - name: "sensitive_file_protection"
    type: policy
    target: "/etc/passwd"
    enforced: true
    violation_action: block
policy_evaluation:
  policy_id: "sys_file_protection"
  result: deny
  conditions_met: []
  conditions_failed:
    - "path must be within workspace"
    - "system files are read-only"
scope_reduction:
  original_scope:
    paths: ["/**"]
  constrained_scope:
    paths: ["/workspace/**"]
  removed_permissions:
    - "write to system paths"
compliant: false
violations:
  - constraint: "workspace_boundary"
    detail: "path must be within workspace"
    action: block
  - constraint: "sensitive_file_protection"
    detail: "system files are read-only"
    action: block
actions_taken:
  - "block: mutate /etc/passwd"
  - "scope reduced to /workspace/**"
blocked_reason: "Action targets system file outside workspace boundary. Editing /etc/passwd is prohibited."
confidence: 1.0
evidence_anchors:
  - "policy:workspace_boundary:path_check"
  - "policy:sys_file_protection:sensitive_paths"
assumptions: []

Evidence pattern: Policy definitions, path matching against workspace boundary.

Example 2: Constrain API Call with Rate Limiting

Input:

yaml

target:
  capability: "send"
  target: "https://api.external.com/data"
  parameters:
    method: "POST"
    payload: {...}
constraints: ["external_api_rate_limit", "checkpoint_before_send"]
action_on_violation: warn

Session abc123 has already made 95 requests this hour.

Output:

yaml

constraints_applied:
  - name: "external_api_rate_limit"
    type: rate_limit
    target: "api.external.com"
    enforced: true
    violation_action: warn
  - name: "checkpoint_before_send"
    type: policy
    target: "send capability"
    enforced: true
    violation_action: block
policy_evaluation:
  policy_id: "external_communication"
  result: conditional
  conditions_met:
    - "destination is allowed domain"
    - "payload size within limits"
  conditions_failed:
    - "approaching rate limit (95/100 this hour)"
scope_reduction:
  original_scope:
    rate_limit: 100
    burst_allowed: true
  constrained_scope:
    rate_limit: 5
    burst_allowed: false
  removed_permissions:
    - "burst requests"
compliant: true
violations:
  - constraint: "external_api_rate_limit"
    detail: "approaching rate limit (95/100 this hour)"
    action: warn
actions_taken:
  - "warn: 95/100 requests used this hour"
  - "scope reduced: rate limit 5, no burst"
blocked_reason: null
confidence: 0.9
evidence_anchors:
  - "policy:external_api_rate_limit:hourly_quota"
  - "context:requests_this_hour:95"
assumptions:
  - "Rate limit counter is accurate"
  - "Hour boundary resets at :00"

Example 3: Constrain Before Execute

Input:

yaml

target:
  capability: "execute"
  target: "refactor_handlers_plan"
  parameters:
    plan_id: "plan_20240115_refactor"
constraints: ["checkpoint_required"]
action_on_violation: block

Output:

yaml

constraints_applied:
  - name: "checkpoint_required"
    type: policy
    target: "execute"
    enforced: true
    violation_action: block
policy_evaluation:
  policy_id: "mutation_safety"
  result: conditional
  conditions_met:
    - "plan exists and is valid"
    - "files in scope are editable"
  conditions_failed:
    - "checkpoint not found for scope"
scope_reduction:
  original_scope:
    mutation_allowed: true
  constrained_scope:
    mutation_allowed: false
  removed_permissions:
    - "file mutation (pending checkpoint)"
compliant: false
violations:
  - constraint: "checkpoint_required"
    detail: "checkpoint not found for scope"
    action: block
actions_taken:
  - "block: execute refactor_handlers_plan until checkpoint exists"
blocked_reason: "This execute step mutates files (requires_checkpoint: true). Call 'checkpoint' first with scope matching the plan."
confidence: 1.0
evidence_anchors:
  - "policy:mutation_safety:checkpoint_gate"
  - "composition_patterns.md:CAVR"
assumptions: []

Verification

Apply the following verification patterns:

[ ] Policy Coverage: All applicable policies were evaluated
[ ] Evidence Grounding: Decisions linked to specific policy conditions
[ ] Scope Reduction Valid: Constrained scope is subset of original
[ ] Safety Boundary Check: No sensitive files in allowed scope

Verification tools: Read (for policy files), Grep (for policy search)

Safety Constraints

mutation: false (constrain is evaluation only)
requires_checkpoint: false
requires_approval: false
risk: low

Capability-specific rules:

Always evaluate workspace boundary policy
Always check for sensitive file patterns (.env, credentials, secrets, .pem, .key)
Apply strictest enforcement when ambiguous
Never downgrade enforcement level silently
Log all policy evaluations for audit

Composition Patterns

Commonly follows:

plan - Constrain the planned actions before checkpoint
critique - After identifying risks, constrain to mitigate

Commonly precedes:

checkpoint - After constrain approves, create checkpoint
send - REQUIRED: constrain before any external communication
execute / mutate - Constrain as part of pre-execution checks (constrain must precede them)

Anti-patterns:

CRITICAL: Never skip constrain before send (no unchecked external comms)
Never ignore blocked_reason and proceed anyway
Never silently weaken policy enforcement
Never evaluate constrain after mutation has begun

Workflow references:

See reference/composition_patterns.md#digital-twin-sync-loop for constrain-before-act
See reference/composition_patterns.md#risk-assessment for constrain placement
See reference/verification_patterns.md#pattern-6-safety-boundary-check for boundary checks

Security

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Source

SKILL.md in the repositoryCheckingskills/constrain/SKILL.md

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