0-uddeshya-0 skill: tool-call-guard
purpose
Validate a tool call before it executes. Catches missing parameters, malformed values, and scope overreach. Blocks bad calls. Warns on irreversible ones. Prevents wasted API calls and accidental side effects.
when_to_use
- Before every external tool call in an agent loop
- Tool call involves writes, deletes, or sends
- Input to the tool comes from user text that might be incomplete or malformed
when_not_to_use
- Simple safe read operations where calling is always correct
- You've already validated this exact call this turn
input
tool_name: string # Tool you're about to call
tool_params: object # Parameters you're about to pass
tool_schema: object # Expected types/requirements (optional — skip validation step if not provided)
task_context: string # Why you're making this call
is_destructive: boolean # Creates, modifies, sends, or deletes data?
output
{
"approved": true | false,
"issues": ["string"],
"safe_to_call": true | false,
"warning": "string | null",
"corrected_params": "object | null"
}
instructions
Check this tool call before it executes.
Validate:
1. NECESSITY: Is this call needed for the task, or can the task be done without it?
2. PARAMETERS: Required params present? Types correct? Values in expected range?
3. SCOPE: Does this call do exactly what the task requires, or could it do more?
4. SIDE EFFECTS: If destructive, is scope limited to what was authorized?
Reject if: required param missing or null, value clearly wrong (negative ID, empty required field, wrong format), call would affect more data than intended.
Warn if: call is approved but irreversible.
Correct if: param has fixable format issue (whitespace, wrong case for enum, missing prefix). Never change values that affect intent.
safe_to_call is false if: not approved, OR is_destructive is true and warning is present.
Return JSON only.
constraints
- Max output tokens: 200
- corrected_params: fix format only, never change intent
- safe_to_call false if destructive + has warning
- If approved AND corrected_params is non-null: always use corrected_params in the actual call, not the original tool_params
example
Input:
tool_name: "delete_user"
tool_params: { "user_id": "", "confirm": true }
tool_schema: { "user_id": "required non-empty string", "confirm": "required boolean" }
task_context: "Delete account for user ID 8821"
is_destructive: true
Output:
{
"approved": false,
"issues": ["user_id is empty — required param missing. Context shows it should be 8821."],
"safe_to_call": false,
"warning": null,
"corrected_params": { "user_id": "8821", "confirm": true }
}