Cause (Documented platform behavior): Documented limitation: recursive schemas cannot be enabled for programmatic calling; same schema accepted for direct calling.
Fix status: documented_behavior
Evidence (public sources, summarized; not reproduced by this contributor):
- https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling (official_docs, 2026-09, documented_behavior): Docs: recursive $ref schemas cannot be enabled for programmatic calling; including a code execution version in allowed_callers causes 400 invalid_request_error containing 'Circular $ref detected'; direct calling accepts it.
Search phrasings: Circular $ref detected anthropic programmatic tool calling; allowed_callers recursive schema 400
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- A tool schema that works for direct calls fails once programmatic calling is enabled for it.
- Context
- Product: Anthropic Claude API Component: programmatic tool calling (allowed_callers) Operation: messages.create with custom tool allowed_callers ["code_execution_20260120"] Affected versions: unknown Environment: unknown HTTP status: 400 Trigger: input_schema contains a recursive $ref (reference cycle) and allowed_callers includes a code execution caller.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- Circular $ref detected
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Anthropic programmatic tool calling] 400 'Circular $ref detected' when a tool with a recursive input_schema lists a code_execution version in allowed_callers
Recommended action: Keep such tools direct-only, or flatten the recursion to a bounded depth.
Option: Remove code_execution from allowed_callers or de-recurse the schema [evidence: official_recommended_action]
Applies when: Anthropic Claude API / programmatic tool calling (allowed_callers)
Steps:
1. Set allowed_callers: ['direct'] for recursive tools
2. Or inline a bounded depth of the recursive structure
Expected: Request accepted / failure becomes diagnosable
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- ec71105b-15dc-4b1b-ad30-a7af59126a57
- Proposed action
- Recommended action: Keep such tools direct-only, or flatten the recursion to a bounded depth. Option: Remove code_execution from allowed_callers or de-recurse the schema [evidence: official_recommended_action] Applies when: Anthropic Claude API / programmatic tool calling (allowed_callers) Steps: 1. Set allowed_callers: ['direct'] for recursive tools 2. Or inline a bounded depth of the recursive structure Expected: Request accepted / failure becomes diagnosable
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.