[CHORE] add docs for initial_custom_fields

[sinankeskin]

Greptile Summary

This PR documents initial custom fields for tracking requests. The main changes are:

• Adds shipment and container custom-field guidance to the API reference.
• Adds the nested initial_custom_fields request schema.
• Adds an example with targeted and shipment-wide container values.

Confidence Score: 4/5

The OpenAPI and TypeScript SDK request contracts need to be synchronized before merging.

• The documentation and OpenAPI examples are internally consistent.
• TypeScript SDK callers cannot represent or send the newly documented request field through createTrackingRequest.

docs/openapi.json and the TypeScript SDK request types

Important Files Changed

Filename	Overview
docs/api-docs/api-reference/tracking-requests/create-a-tracking-request.mdx	Adds usage guidance and an example for shipment, targeted-container, and all-container custom fields.
docs/openapi.json	Adds the request schema and example, but the checked-in TypeScript SDK does not expose the new field.

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
docs/openapi.json:1336
**SDK Contract Omits New Field**

The OpenAPI request now exposes `initial_custom_fields`, but the checked-in TypeScript SDK's `createTrackingRequest` parameters do not accept or forward it. SDK callers following this contract receive an excess-property type error or cannot send the custom fields, so the generated types and public client method need to be updated with this schema change.

_{Reviews (1): Last reviewed commit: "chore: Auto-generate Postman collection ..." | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

[linear-code]

DEV-10929

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[greptile-apps]

SDK Contract Omits New Field

The OpenAPI request now exposes initial_custom_fields, but the checked-in TypeScript SDK's createTrackingRequest parameters do not accept or forward it. SDK callers following this contract receive an excess-property type error or cannot send the custom fields, so the generated types and public client method need to be updated with this schema change.

Prompt To Fix With AI

This is a comment left during a code review.
Path: docs/openapi.json
Line: 1336

Comment:
**SDK Contract Omits New Field**

The OpenAPI request now exposes `initial_custom_fields`, but the checked-in TypeScript SDK's `createTrackingRequest` parameters do not accept or forward it. SDK callers following this contract receive an excess-property type error or cannot send the custom fields, so the generated types and public client method need to be updated with this schema change.

How can I resolve this? If you propose a fix, please make it concise.

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Project	Status	Preview	Updated (UTC)
terminal49	🟡 Building	–	Jul 17, 2026, 4:31 PM