NLP Lineage

13 June 2023 · Representation and retrieval

Function calling

Function calling in the OpenAI API

OpenAI

Date
13 June 2023
What the date marks
Announcement
Kind
Product
Organisation
OpenAI
Access
API only
Threads
In the guided tour
Chapter 13. Models that act
Learning phases
3. API usage and prompting; 7. Agents

A milestone: 1 later milestone descends directly from it, and its descendants reach 5 of the 10 threads. How levels are decided

Read the primary source (openai.com)

Full summary in progress. Until then, this page shows the milestone's record from the research data.

What it changed

Before it

Developers coaxed structured tool calls out of models with prompt templates and regex parsing.

The problem

Free-text tool calls are unreliable to parse and break silently.

What it introduced

Declare functions with a JSON schema; the model returns a structured call the runtime can execute.

Why it matters

It turned agents from a research pattern into ordinary application development.

What modern models inherit

Structured tool calling as a basic API feature.

What came next

MCP standardised the connection between models and tools a year later.

Before and after

The milestones it descends from, and the milestones that descend from it. Work developed alongside it is not counted. Weak links are left out unless you include them.

Before: where it came from

No documented ancestors are recorded for Function calling without weak links.

No documented ancestors are recorded for Function calling without weak links.

Function calling has 34 recorded ancestors, including indirect ones, across 8 chapters, reaching back to Recurrent networks in 1990. Showing its direct parents and the 11 turning points among them.

Function calling has 34 recorded ancestors, including indirect ones, across 8 chapters, reaching back to Recurrent networks in 1990. Showing all of them.

  1. 2023Function callingThis milestone.
  2. 2023ToolformerFunction calling was influenced by this (indirect influence)Chapter 13. Models that act
  3. 2022ReActFunction calling was influenced by this (indirect influence)Chapter 13. Models that act
  4. 2022Chain of thought Turning pointReAct built directly on thisChapter 12. Thinking longer
  5. 2021WebGPTReAct was influenced by this
    Toolformer was influenced by this    Chapter 13. Models that act
  6. 2020RLHF for summarisation Turning pointWebGPT built directly on thisChapter 6. Teaching models what people want
  7. 2020GPT-3 Turning pointToolformer built directly on thisChapter 5. Scale becomes a science
  8. 2020Scaling laws Turning pointGPT-3 was influenced by thisChapter 5. Scale becomes a science
  9. 2019RLHF for LMsRLHF for summarisation built directly on thisChapter 6. Teaching models what people want
  10. 2019Sparse Transformer Turning pointGPT-3 built directly on thisChapter 4. Pretrain once, use everywhere
  11. 2019GPT-2 Turning pointGPT-3 built directly on thisChapter 4. Pretrain once, use everywhere
  12. 2019WebTextGPT-2 was influenced by thisChapter 4. Pretrain once, use everywhere
  13. 2019Transformer-XLSparse Transformer was influenced by this (indirect influence)Chapter 4. Pretrain once, use everywhere
  14. 2018GPT-1GPT-2 built directly on thisChapter 4. Pretrain once, use everywhere
  15. 2018ELMoGPT-1 was influenced by this (indirect influence)Chapter 4. Pretrain once, use everywhere
  16. 2018ULMFiTGPT-1 was influenced by this (indirect influence)Chapter 4. Pretrain once, use everywhere
  17. 2017CoVeELMo was influenced by thisChapter 3. Attention, then only attention
  18. 2017RLHF originRLHF for summarisation built directly on thisChapter 6. Teaching models what people want
  19. 2017Transformer Turning pointGPT-2 built directly on this
    Sparse Transformer built directly on this
    Scaling laws built directly on this    Chapter 3. Attention, then only attention
  20. 2017ConvS2STransformer was influenced by this (indirect influence)Chapter 3. Attention, then only attention
  21. 2016Layer normGPT-2 built directly on thisChapter 3. Attention, then only attention
  22. 2015Residual connectionsTransformer was influenced by thisChapter 3. Attention, then only attention
  23. 2015LM pretraining Turning pointGPT-1 was influenced by thisChapter 2. Words become vectors
  24. 2015BPE tokenizationGPT-2 built directly on thisChapter 2. Words become vectors
  25. 2015Luong attentionTransformer was influenced by thisChapter 3. Attention, then only attention
  26. 2014AdamTransformer was influenced by thisChapter 2. Words become vectors
  27. 2014GloVeELMo built directly on thisChapter 2. Words become vectors
  28. 2014Seq2seq Turning pointTransformer built directly on thisChapter 2. Words become vectors
  29. 2014Attention Turning pointTransformer built directly on thisChapter 3. Attention, then only attention
  30. 2014GRU / encoder-decoderAttention built directly on thisChapter 2. Words become vectors
  31. 2013word2vecELMo was influenced by thisChapter 2. Words become vectors
  32. 2011NLP from scratchELMo was influenced by thisChapter 1. Language as probability
  33. 2003Neural LMNLP from scratch was influenced by this
    word2vec was influenced by this    Chapter 1. Language as probability
  34. 1997LSTM Turning pointSeq2seq built directly on this
    ELMo built directly on this    Chapter 1. Language as probability
  35. 1990Recurrent networksLSTM was influenced by thisChapter 1. Language as probability

After: what it led to

Function calling has 10 documented descendants across 4 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing its direct descendants.

Function calling has 10 documented descendants across 4 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing all of them.

Function calling has 22 recorded descendants, including indirect ones, across 4 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing its direct descendants.

Function calling has 22 recorded descendants, including indirect ones, across 4 chapters, reaching forward to GPT-5.6 Sol in 2026. Showing all of them.

  1. 2023Function callingThis milestone.
  2. 2025Deep researchwas influenced by o3 releasedChapter 13. Models that act
  3. 2025o3 releasedwas influenced by Function callingChapter 12. Thinking longer
  4. 2025gpt-ossbuilt directly on o3 releasedChapter 8. The weights get out
  5. 2025GPT-5built directly on o3 releasedChapter 14. Where the threads meet now
  6. 2025GPT-5.1built directly on GPT-5Chapter 14. Where the threads meet now
  7. 2025GPT-5.2built directly on GPT-5.1Chapter 14. Where the threads meet now
  8. 2026GPT-5.3-Codexbuilt directly on GPT-5.2Chapter 13. Models that act
  9. 2026GPT-5.4built directly on GPT-5.3-CodexChapter 14. Where the threads meet now
  10. 2026GPT-5.5built directly on GPT-5.4Chapter 14. Where the threads meet now
  11. 2026GPT-5.6 Solbuilt directly on GPT-5.5Chapter 14. Where the threads meet now
  1. 2023Function callingThis milestone.
  2. 2024Computer usewas influenced by Function calling (indirect influence)Chapter 13. Models that act
  3. 2024MCPwas influenced by Function calling (indirect influence)Chapter 13. Models that act
  4. 2024Gemini 2.0was influenced by Computer use (indirect influence)Chapter 14. Where the threads meet now
  5. 2025Deep researchwas influenced by o3 releasedChapter 13. Models that act
  6. 2025Claude Codewas influenced by Computer use
    was influenced by MCP    Chapter 13. Models that act
  7. 2025Gemini 2.5built directly on Gemini 2.0Chapter 12. Thinking longer
  8. 2025o3 releasedwas influenced by Function callingChapter 12. Thinking longer
  9. 2025IMO goldbuilt directly on Gemini 2.5Chapter 12. Thinking longer
  10. 2025gpt-ossbuilt directly on o3 releasedChapter 8. The weights get out
  11. 2025GPT-5built directly on o3 releasedChapter 14. Where the threads meet now
  12. 2025IMO-ProofBenchwas influenced by IMO goldChapter 12. Thinking longer
  13. 2025GPT-5.1built directly on GPT-5Chapter 14. Where the threads meet now
  14. 2025Gemini 3built directly on Gemini 2.5Chapter 14. Where the threads meet now
  15. 2025GPT-5.2built directly on GPT-5.1Chapter 14. Where the threads meet now
  16. 2026GPT-5.3-Codexwas influenced by Computer use (indirect influence)Chapter 13. Models that act
  17. 2026Gemini 3 Deep Thinkbuilt directly on Gemini 3
    was influenced by IMO gold    Chapter 12. Thinking longer
  18. 2026Gemini 3.1built directly on Gemini 3Chapter 14. Where the threads meet now
  19. 2026GPT-5.4built directly on GPT-5.3-CodexChapter 14. Where the threads meet now
  20. 2026Project Glasswingwas influenced by Computer use (indirect influence)Chapter 14. Where the threads meet now
  21. 2026GPT-5.5built directly on GPT-5.4Chapter 14. Where the threads meet now
  22. 2026Fable 5 / Mythos 5was influenced by Project GlasswingChapter 14. Where the threads meet now
  23. 2026GPT-5.6 Solbuilt directly on GPT-5.5Chapter 14. Where the threads meet now

Direct links and their sources

Where it came from

Influenced by

What it led to

Influenced