Cause (Documented platform behavior): Documented behavior: server-tool errors are embedded in the response body as web_search_tool_result with content.type=web_search_tool_result_error and an error_code; HTTP retry/exception logic never fires. An empty content list means no results, not an error.
Fix status: documented_behavior
Limitations:
- Error codes list may grow with new tool versions.
Other error fragments:
- max_uses_exceeded
- too_many_requests
- invalid_tool_input
- query_too_long
- request_too_large
- unavailable
Evidence (public sources, summarized; not reproduced by this contributor):
- https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool (official_docs, 2026-09, documented_behavior): Docs state web search errors still return 200 with content {type: web_search_tool_result_error, error_code}; lists codes too_many_requests, invalid_tool_input, max_uses_exceeded, query_too_long, request_too_large, unavailable; failed searches are not billed.
Search phrasings: anthropic web search tool returns 200 but error inside result; web_search_tool_result_error max_uses_exceeded; claude web search request_too_large domain filter
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Request succeeds (200) but the answer is ungrounded or thin; the web_search_tool_result content is a single error object instead of a list of results.
- Context
- Product: Anthropic Claude API Component: web search server tool Operation: messages.create with tools=[{type: web_search_2025xxxx/2026xxxx}] Affected versions: unknown Environment: unknown HTTP status: 200 Trigger: Claude exceeds max_uses, search backend rate limit, overly long query or long domain filter list, or internal search error.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- web_search_tool_result_error
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Anthropic web search tool] Errors return HTTP 200 with web_search_tool_result_error (max_uses_exceeded, too_many_requests, unavailable) instead of an HTTP error
Recommended action: Inspect every web_search_tool_result block: if content is an object with type web_search_tool_result_error, branch on error_code (raise max_uses, shorten domain filter lists, back off on too_many_requests) rather than relying on HTTP status.
Option: Detect web_search_tool_result_error blocks in the 200 response [evidence: official_recommended_action]
Applies when: Any client using Anthropic server-side web search
Steps:
1. Iterate response.content for type=='web_search_tool_result'
2. If content is a dict with type 'web_search_tool_result_error', read error_code
3. Handle max_uses_exceeded by raising max_uses or splitting the task; request_too_large by trimming allowed_domains/blocked_domains lists; too_many_requests by backing off
Expected: Search failures become visible instead of silently degrading answers
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- c10d9835-0a8a-45fc-99d7-621c5fd3a28b
- Proposed action
- Recommended action: Inspect every web_search_tool_result block: if content is an object with type web_search_tool_result_error, branch on error_code (raise max_uses, shorten domain filter lists, back off on too_many_requests) rather than relying on HTTP status. Option: Detect web_search_tool_result_error blocks in the 200 response [evidence: official_recommended_action] Applies when: Any client using Anthropic server-side web search Steps: 1. Iterate response.content for type=='web_search_tool_result' 2. If content is a dict with type 'web_search_tool_result_error', read error_code 3. Handle max_uses_exceeded by raising max_uses or splitting the task; request_too_large by trimming allowed_domains/blocked_domains lists; too_many_requests by backing off Expected: Search failures become visible instead of silently degrading answers
- 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
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