Phone Line Type Checker API Workflow for Automated Checks

What the pipeline has to decide for every number

This isn’t a theory page — it’s about building an automated pipeline for line type verification. Mobile, landline, VoIP, toll-free: if your system needs to know which category a phone number falls into without manual intervention, you need the API.

Phone Line Type Checker on ZelNum provides this. But the integration matters more than the endpoint. Here’s the pattern that holds up in production.

Integration shape

Treat the API workflow as a job, not a single magic call. Submit the batch, store the task ID, poll or receive completion, then join results back to source.

Example request

{
  "job_type": "phone_line_type_checker_api_workflow",
  "source": "crm_export_2026_07",
  "input_column": "phone",
  "row_id_column": "record_id",
  "callback_url": "https://example.com/hooks/check-completeZelNum/callback"
}

Response fields worth keeping

Retry and cost rules

Don’t retry every failed row. Retry timeouts and temporary unknowns. Don’t retry rows that failed because the input was empty, badly formatted, or outside supported markets.

• Cap retries per record
• Store the first failure reason — don’t overwrite it
• Run a small batch after every parser or upload change
• Track cost per usable row, not total lookup cost alone

Roll out safely

Start with CSV if the workflow is still being designed. Move to API only after the result fields and routing rules are stable. That keeps developers from hard-coding decisions the operations team hasn’t agreed on.

Test file setup

Before committing to the full list, run a test batch. When the output can’t influence a routing path, a retry window, or a cleanup script, running the check at scale probably isn’t worth it.

record_id,phone,source,segment
crm_40148,+13125550731,form_fills,signups_q2
crm_40264,020 4571 0938,past_import,customer_base
crm_40376,+61491570156,partner_upload,leads

Result groups built for action

Settle on these rules ahead of the full run, or the result file ends up as one more spreadsheet waiting for interpretation.

Settle these before writing code

Before the API path gets built, nail down the payload shape, the response fields, and the retry logic. Developers can work with a narrow spec. They can’t work with a vague status field that means different things to different teams.

• Demonstrate that the source row ID makes it through the whole job
• Draw a line between temporary errors and permanent input problems
• Describe polling, callback, or export retrieval without jargon
• Point the API flow back to the product page — keep the product promise in one place

When the file isn’t ready yet

Tool availability alone is no reason to run a lookup. Pass on it when the file is too small for batch work, when the source data lacks the input column, or when the result can’t affect your next action.

FAQ

Do I need an API for line type checking?

Use an API when the check is part of a product flow, scheduled job, or internal data pipeline. For one-time uploads, CSV is usually faster to start. Most teams begin with CSV and add API when volume demands it.

Which fields should I store?

Keep the source row ID, original input, normalized value, status, reason code, and checked timestamp, plus the product-specific fields: line_type, carrier, country_or_region. These six plus your internal identifiers are the minimum for a production-ready pipeline.

How should I handle unknown results?

Keep unknowns out of the failed bucket. Retry once, then route valuable records to manual review or a slower fallback workflow. Unknown ≠ bad — and deleting unknowns deletes records a retry would recover.

Related ZelNum pages

• ZelNum product directory
• Phone Line Type Checker
• ZelNum API
• ZelNum pricing

Try Phone Line Type Checker →

Related articles

• our landline-vs-mobile breakdown
• this carrier-identification walkthrough