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fix(AIC-3577): send object tool results to the model as JSON - #188

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fix(AIC-3577): send object tool results to the model as JSON#188
jeffdupont merged 1 commit into
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jdupont/aic-3577-tool-result-string

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@jeffdupont jeffdupont commented Oct 20, 2026 •
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Fixes AIC-3577.

Why

When a tool handler returns a dict (say {"temp": 72}), every handler sent it back to the model through str(result). The model then read the Python repr ({'temp': 72}, with single quotes) instead of JSON, and other values such as True or None reached it in Python syntax too. The Go SDK already gets this right (aiserver.ToolResultString, aiserver/handlerkit.go): a string passes through, nil becomes "", anything else is JSON. This PR applies the same rule here.

Fix

  • New public tool_result_string in launchdarkly_ai_server/content.py, exported from the package: a string is unchanged, None becomes "", anything else goes through json.dumps(value, ensure_ascii=False). A value it cannot encode falls back to str(value). The private _stringify_tool_value used for span capture is unchanged.
  • Every tool-result site now uses it in place of str(result): claude-messages, openai-messages (invoke and stream, including the text the stream reports) and langchain-messages handlers, openai-agents (FunctionTool return and stream hook) and langchain-agents handlers and native graphs, and claude-agents.
  • tests/test_public_surface.py lists the new export.
  • openai-agents/tests/test_handler.py::test_sync_tool_handler_result_is_returned asserted str(dict), which is the bug. It now expects json.dumps(dict).

Testing

  • New: tool_result_string tests in packages/client/tests/test_content.py (string, dict with non-ASCII, list, number, None, cyclic dict, set), plus test_object_tool_result_reaches_the_model_as_json in packages/openai-messages/tests/test_handler.py, which checks the second responses.create input carries {"temp": 72, "city": "Zürich"}.
  • With the fix reverted: the handler test fails ("{'temp': 72,...y': 'Zürich'}" == '{"temp": 72,...y": "Zürich"}') and the client tests fail to import tool_result_string.
  • make test: 2547 passed, 14 skipped. make typecheck: no issues in 75 source files. make lint and make format-check: pass.

Related: launchdarkly/js-ai-sdk#146 (JS), https://github.com/launchdarkly/ai-sdks-monorepo/pull/72 (spec)

🤖 Generated with Claude Code

@jeffdupont @claude
fix(AIC-3577): send object tool results to the model as JSON
d756beb 
Handlers stringified tool results with str(), so a dict reached the model as its Python repr. Add tool_result_string to the client (string unchanged, None to empty, else json.dumps with ensure_ascii=False) and use it at every tool-result site, matching Go ToolResultString.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
@jeffdupont jeffdupont mentioned this pull request Oct 20, 2026
Merged
@jeffdupont
jeffdupont requested a review from a team October 21, 2026 15:20
@jeffdupont
jeffdupont merged commit dead4bd into main Oct 21, 2026
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@jeffdupont
jeffdupont deleted the jdupont/aic-3577-tool-result-string branch October 21, 2026 20:12
@github-actions github-actions Bot mentioned this pull request Oct 21, 2026
Merged
jeffdupont pushed a commit that referenced this pull request Oct 23, 2026
@github-actions
chore: release main (#166)
662d3f2 
🤖 I have created a release *beep* *boop*
---


<details><summary>launchdarkly-ai-server: 0.4.0</summary>

##
[0.4.0](launchdarkly-ai-server-0.3.0...launchdarkly-ai-server-0.4.0)
(2026-10-23)


### ⚠ BREAKING CHANGES

* **evaluations:** keep the management API client internal
([#202](#202))
* **evaluations:** rename base uri to match spec
([#199](#199))
* **evaluations:** add test proving harness edge case matches spec
([#200](#200))
* **evaluations:** route handlers by provider and mode
* **evaluations:** mark evaluations from code as experimental
([#157](#157))

### Experimental

* **evaluations:** add test proving harness edge case matches spec
([#200](#200))
([fa7162e](fa7162e))
* **evaluations:** keep the management API client internal
([#202](#202))
([17270ed](17270ed))
* **evaluations:** mark evaluations from code as experimental
([#157](#157))
([1389765](1389765))
* **evaluations:** rename base uri to match spec
([#199](#199))
([7d93f9c](7d93f9c))
* **evaluations:** route handlers by provider and mode
([f62591f](f62591f))
* **evaluations:** Set JSON as standard for output to pass to judge
([#203](#203))
([ffc728b](ffc728b))
* **skills:** Correct the HTTP 403 advice now that server-side FDv2 is
available to every account
([#178](#178))
([b17e322](b17e322))


### Features

* **agui:** add a shared reader for handler streams
([#164](#164))
([fc08dd5](fc08dd5))
* **AIC-3534:** add a TypeSafe Jev judge handler
([#149](#149))
([1b41ea4](1b41ea4))
* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))
* **langchain:** emit AG-UI text and tool events
([#163](#163))
([ab5e9e1](ab5e9e1))
* **openai:** emit AG-UI text and tool events
([#161](#161))
([2b1b2d4](2b1b2d4))


### Bug Fixes

* **AIC-3570:** re-resolve graph flags on every invoke and stream
([#187](#187))
([8fdc4d4](8fdc4d4))
* **AIC-3571:** visit every child before its parent in reverse_traverse
([#189](#189))
([87c73d9](87c73d9))
* **AIC-3572:** treat a variation without _ldMeta.enabled as disabled
([#184](#184))
([7a0d260](7a0d260))
* **AIC-3574:** build the LaunchDarkly client off the event loop
([#185](#185))
([bf03b6c](bf03b6c))
* **AIC-3576:** record deferred judge scores under the evaluated config
([#190](#190))
([354d3f1](354d3f1))
* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
* **AIC-3596:** name the [otel] extra in the missing-OTel warning
([#186](#186))
([90ce7bf](90ce7bf))
* **client:** match a handler's provides_for after normalizing its mode
([f62591f](f62591f))
* give native graph spans their LaunchDarkly identity
([#121](#121))
([e863b6d](e863b6d))
</details>

<details><summary>launchdarkly-ai-python: 0.3.0</summary>

##
[0.3.0](launchdarkly-ai-python-0.2.0...launchdarkly-ai-python-0.3.0)
(2026-10-23)


### ⚠ BREAKING CHANGES

* **evaluations:** mark evaluations from code as experimental
([#157](#157))

### Experimental

* **evaluations:** mark evaluations from code as experimental
([#157](#157))
([1389765](1389765))
</details>

<details><summary>launchdarkly-ai-claude-agents: 0.2.6</summary>

##
[0.2.6](launchdarkly-ai-claude-agents-0.2.5...launchdarkly-ai-claude-agents-0.2.6)
(2026-10-23)


### Features

* **claude:** emit AG-UI text and tool events
([#165](#165))
([3f3a0ce](3f3a0ce))
* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))


### Bug Fixes

* **AIC-3571:** visit every child before its parent in reverse_traverse
([#189](#189))
([87c73d9](87c73d9))
* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
* **claude-agents:** fail the run when the CLI reports an API error as
success
([#174](#174))
([3d1a768](3d1a768))
* give native graph spans their LaunchDarkly identity
([#121](#121))
([e863b6d](e863b6d))
</details>

<details><summary>launchdarkly-ai-claude-messages: 0.2.5</summary>

##
[0.2.5](launchdarkly-ai-claude-messages-0.2.4...launchdarkly-ai-claude-messages-0.2.5)
(2026-10-23)


### Features

* **claude:** emit AG-UI text and tool events
([#165](#165))
([3f3a0ce](3f3a0ce))
* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))


### Bug Fixes

* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
</details>

<details><summary>launchdarkly-ai-openai-agents: 0.2.6</summary>

##
[0.2.6](launchdarkly-ai-openai-agents-0.2.5...launchdarkly-ai-openai-agents-0.2.6)
(2026-10-23)


### Features

* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))
* **openai:** emit AG-UI text and tool events
([#161](#161))
([2b1b2d4](2b1b2d4))


### Bug Fixes

* **AIC-3571:** visit every child before its parent in reverse_traverse
([#189](#189))
([87c73d9](87c73d9))
* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
* give native graph spans their LaunchDarkly identity
([#121](#121))
([e863b6d](e863b6d))
</details>

<details><summary>launchdarkly-ai-vercel-agents: 0.1.1</summary>

##
[0.1.1](launchdarkly-ai-vercel-agents-0.1.0...launchdarkly-ai-vercel-agents-0.1.1)
(2026-10-23)


### Features

* **AIC-3408:** add Vercel AI SDK messages and agents adapters
([#103](#103))
([64d679e](64d679e))
</details>

<details><summary>launchdarkly-ai-litellm-agents: 0.1.1</summary>

##
[0.1.1](launchdarkly-ai-litellm-agents-0.1.0...launchdarkly-ai-litellm-agents-0.1.1)
(2026-10-23)


### Features

* add LiteLLM messages and agents integrations
([#102](#102))
([f2e9886](f2e9886))
</details>

<details><summary>launchdarkly-ai-openai-messages: 0.2.5</summary>

##
[0.2.5](launchdarkly-ai-openai-messages-0.2.4...launchdarkly-ai-openai-messages-0.2.5)
(2026-10-23)


### Features

* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))
* **openai:** emit AG-UI text and tool events
([#161](#161))
([2b1b2d4](2b1b2d4))


### Bug Fixes

* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
</details>

<details><summary>launchdarkly-ai-vercel-messages: 0.1.1</summary>

##
[0.1.1](launchdarkly-ai-vercel-messages-0.1.0...launchdarkly-ai-vercel-messages-0.1.1)
(2026-10-23)


### Features

* **AIC-3408:** add Vercel AI SDK messages and agents adapters
([#103](#103))
([64d679e](64d679e))
</details>

<details><summary>launchdarkly-ai-litellm-messages: 0.1.1</summary>

##
[0.1.1](launchdarkly-ai-litellm-messages-0.1.0...launchdarkly-ai-litellm-messages-0.1.1)
(2026-10-23)


### Features

* add LiteLLM messages and agents integrations
([#102](#102))
([f2e9886](f2e9886))
</details>

<details><summary>launchdarkly-ai-langchain-agents: 0.2.6</summary>

##
[0.2.6](launchdarkly-ai-langchain-agents-0.2.5...launchdarkly-ai-langchain-agents-0.2.6)
(2026-10-23)


### Features

* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))
* **langchain:** emit AG-UI text and tool events
([#163](#163))
([ab5e9e1](ab5e9e1))


### Bug Fixes

* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
* give native graph spans their LaunchDarkly identity
([#121](#121))
([e863b6d](e863b6d))
</details>

<details><summary>launchdarkly-ai-langchain-messages: 0.2.5</summary>

##
[0.2.5](launchdarkly-ai-langchain-messages-0.2.4...launchdarkly-ai-langchain-messages-0.2.5)
(2026-10-23)


### Features

* **client:** add configure for SDK defaults
([#158](#158))
([3736767](3736767))
* **langchain:** emit AG-UI text and tool events
([#163](#163))
([ab5e9e1](ab5e9e1))


### Bug Fixes

* **AIC-3577:** send object tool results to the model as JSON
([#188](#188))
([dead4bd](dead4bd))
</details>

<details><summary>launchdarkly-ai-opencode-agents: 0.2.0</summary>

##
[0.2.0](launchdarkly-ai-opencode-agents-0.1.0...launchdarkly-ai-opencode-agents-0.2.0)
(2026-10-23)


### ⚠ BREAKING CHANGES

* **opencode:** start and stop opencode serve in the handler
([#198](#198))

### Features

* **opencode-agents:** add an OpenCode handler
([#159](#159))
([fc08e8c](fc08e8c))
* **opencode-agents:** emit the AG-UI text and tool subset
([#162](#162))
([7677621](7677621))
* **opencode-agents:** open one OpenCode session per call
([#179](#179))
([b225113](b225113))
* **opencode-agents:** render agent instruction templates
([#182](#182))
([83175aa](83175aa))
* **opencode:** start and stop opencode serve in the handler
([#198](#198))
([0748dcf](0748dcf))


### Bug Fixes

* **opencode-agents:** own the HTTP client
([#194](#194))
([ed2d419](ed2d419))
* **opencode-agents:** skip judges and record structured history
([#177](#177))
([6fadf1d](6fadf1d))
</details>

<details><summary>launchdarkly-ai-typesafe: 0.1.1</summary>

##
[0.1.1](launchdarkly-ai-typesafe-0.1.0...launchdarkly-ai-typesafe-0.1.1)
(2026-10-23)


### Features

* **AIC-3534:** add a TypeSafe Jev judge handler
([#149](#149))
([1b41ea4](1b41ea4))
</details>

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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@jeffdupont @andrewklatzke