Pydantic TypeAdapter.json_schema drops `description` from

The Fix

pip install pydantic==1.10.19

Based on closed pydantic/pydantic issue #9404 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Jump to Verify Open PR/Commit

@@ -1569,9 +1569,8 @@ def _generate_parameter_schema(
             field = FieldInfo.from_annotated_attribute(annotation, default)
         assert field.annotation is not None, 'field.annotation should not be None when generating a schema'
-        source_type, annotations = field.annotation, field.metadata
         with self.field_name_stack.push(name):
-            schema = self._apply_annotations(source_type, annotations)

repro.py

pydantic version: 2.7.1
        pydantic-core version: 2.18.2
          pydantic-core build: profile=release pgo=false
                 install path: /Users/charlesstern/miniconda3/envs/ecoscope/lib/python3.10/site-packages/pydantic
               python version: 3.10.12 | packaged by conda-forge | (main, Jun 23 2023, 22:39:40) [Clang 15.0.7 ]
                     platform: macOS-14.4.1-x86_64-i386-64bit
             related packages: typing_extensions-4.11.0
                       commit: unknown

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install pydantic==1.10.19\nWhen NOT to use: Do not apply this fix if the schema generation behavior is intended to differ for functions.\n\nOption C — Workaround\nusing a subclass of `GenerateJsonSchema`.\nWhen NOT to use: Do not apply this fix if the schema generation behavior is intended to differ for functions.\n\n

Why This Fix Works in Production

Trigger: TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a function
Mechanism: The `description` attribute of an Annotated Field is dropped when the type is a plain function
Why the fix works: Fixes the issue where the `description` attribute of an Annotated Field is dropped when the type is a function. (first fixed release: 1.10.19).

Production impact:

If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.

Why This Breaks in Prod

Shows up under Python 3.10 in real deployments (not just unit tests).
The `description` attribute of an Annotated Field is dropped when the type is a plain function
Production symptom (often without a traceback): TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a function

Proof / Evidence

GitHub issue: #9404
Fix PR: https://github.com/pydantic/pydantic/pull/10610
First fixed release: 1.10.19
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.53

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“Working on this now. It's quite messy, lots of core schema issues for parameters. Should have a fix done by the end of the week.”

@sydney-runkle · 2024-05-21 · source

“Hi @cisaacstern, Thanks for your kind words. We really appreciate the in-depth description and MRE :). Thanks for reporting this - definitely looks like a…”

@sydney-runkle · 2024-05-16 · source

“@sydney-runkle, thanks for your reply! Yes, I would be happy to make a PR. I will ping back here when I have one for review…”

@cisaacstern · 2024-05-16 · source

“@cisaacstern, Fantastic! Sorry for the delayed response last week, was out for vacation.”

@sydney-runkle · 2024-05-16 · source

Failure Signature (Search String)

TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a function
The MRE provided below demonstrates this issue and a workaround using a subclass of `GenerateJsonSchema`.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a function
The MRE provided below demonstrates this issue and a workaround using a subclass of `GenerateJsonSchema`.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a function
The MRE provided below demonstrates this issue and a workaround using a subclass of `GenerateJsonSchema`.

Minimal Reproduction

repro.py

pydantic version: 2.7.1
        pydantic-core version: 2.18.2
          pydantic-core build: profile=release pgo=false
                 install path: /Users/charlesstern/miniconda3/envs/ecoscope/lib/python3.10/site-packages/pydantic
               python version: 3.10.12 | packaged by conda-forge | (main, Jun 23 2023, 22:39:40) [Clang 15.0.7 ]
                     platform: macOS-14.4.1-x86_64-i386-64bit
             related packages: typing_extensions-4.11.0
                       commit: unknown

Environment

Python: 3.10
Pydantic: 2

What Broke

Generated JSON Schema lacks expected descriptions for fields, leading to potential confusion.

Why It Broke

The `description` attribute of an Annotated Field is dropped when the type is a plain function

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install pydantic==1.10.19

When NOT to use: Do not apply this fix if the schema generation behavior is intended to differ for functions.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Option C — Workaround Temporary workaround

using a subclass of `GenerateJsonSchema`.

When NOT to use: Do not apply this fix if the schema generation behavior is intended to differ for functions.

Use only if you cannot change versions today. Treat this as a stopgap and remove once upgraded.

Fix reference: https://github.com/pydantic/pydantic/pull/10610

First fixed release: 1.10.19

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

Do not apply this fix if the schema generation behavior is intended to differ for functions.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
Upgrade behind a canary and run integration tests against the canary before 100% rollout.

Version Compatibility Table

Version	Status
1.10.19	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:configuration-error Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Data consistency OpenAPI schema Serialization

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Pydantic TypeAdapter.json_schema drops `description` from Annotated Fields when self.type is a (Fix)