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AI skills glossary · Building with LLMs

Tool use (function calling)

Letting a language model call external functions and APIs — search, databases, code execution — by emitting structured requests the application then runs.

Hiring data as of November 14, 2026, refreshed daily. All terms in the AI skills glossary

companies naming it
11 of 47companies naming it
open roles naming it
13open roles naming it
of those based in NYC
8of those based in NYC
pay: under 8 posted ranges
—pay: under 8 posted ranges

What Tool use means

Tool use, also called function calling, is how a language model acts on anything outside its own text. The application describes the available functions; the model responds with a structured request to call one; the application executes it and returns the result for the model to continue with. It is the mechanism underneath every agent.

The craft is in tool design: what each tool is named, how its parameters are described, what it returns on failure. A model can only be as reliable as the tools are legible to it, and a badly described tool produces errors that look like model mistakes.

Tool use in New York job posts

11 of the 47 New York AI companies we track name Tool use in at least one open role today, across 13 postings. 8 of those are based in New York; the rest are remote or in the companies’ other offices.

This is engineering vocabulary: 69% of the postings that name it are Engineering roles.

How to read it

Almost always appears next to AI agents and evals, in postings for engineers building agent platforms. It indicates hands-on agent work rather than chat-interface work. Expect design questions: how you would expose an internal API to a model, and how you would stop it being called in ways you did not intend.

What these roles pay

Not enough data to publish. We need at least eight distinct posted salary ranges on New York roles naming Tool use before showing a median, and today there are fewer. For posted pay by function and seniority across the whole market, use the NYC salary calculator or the NYC AI engineer salary guide.

Companies naming Tool use, daily

Count of companies with at least one open role naming the term. We read between 46 and 47 companies a day over this period, so a move of one or two is noise.

07.51511Sep 20Nov 14Sep 20: 10 companiesSep 21: 10 companiesSep 22: 10 companiesSep 23: 10 companiesSep 24: 10 companiesSep 25: 9 companiesSep 26: 9 companiesSep 27: 9 companiesSep 28: 8 companiesSep 29: 9 companiesSep 30: 8 companiesOct 1: 8 companiesOct 2: 8 companiesOct 3: 8 companiesOct 4: 8 companiesOct 5: 8 companiesOct 6: 8 companiesOct 7: 10 companiesOct 8: 10 companiesOct 9: 10 companiesOct 10: 10 companiesOct 11: 10 companiesOct 12: 10 companiesOct 13: 10 companiesOct 14: 10 companiesOct 15: 10 companiesOct 16: 10 companiesOct 17: 10 companiesOct 18: 10 companiesOct 19: 10 companiesOct 20: 10 companiesOct 21: 10 companiesOct 22: 11 companiesOct 23: 11 companiesOct 24: 11 companiesOct 25: 11 companiesOct 26: 11 companiesOct 27: 11 companiesOct 28: 11 companiesOct 29: 11 companiesOct 30: 11 companiesOct 31: 11 companiesNov 1: 11 companiesNov 2: 11 companiesNov 3: 12 companiesNov 4: 12 companiesNov 5: 11 companiesNov 6: 10 companiesNov 7: 10 companiesNov 8: 10 companiesNov 9: 10 companiesNov 10: 10 companiesNov 11: 10 companiesNov 12: 11 companiesNov 13: 11 companiesNov 14: 11 companies
View as table
Datecompanies
2026-09-2010
2026-09-2110
2026-09-2210
2026-09-2310
2026-09-2410
2026-09-259
2026-09-269
2026-09-279
2026-09-288
2026-09-299
2026-09-308
2026-10-018
2026-10-028
2026-10-038
2026-10-048
2026-10-058
2026-10-068
2026-10-0710
2026-10-0810
2026-10-0910
2026-10-1010
2026-10-1110
2026-10-1210
2026-10-1310
2026-10-1410
2026-10-1510
2026-10-1610
2026-10-1710
2026-10-1810
2026-10-1910
2026-10-2010
2026-10-2110
2026-10-2211
2026-10-2311
2026-10-2411
2026-10-2511
2026-10-2611
2026-10-2711
2026-10-2811
2026-10-2911
2026-10-3011
2026-10-3111
2026-11-0111
2026-11-0211
2026-11-0312
2026-11-0412
2026-11-0511
2026-11-0610
2026-11-0710
2026-11-0810
2026-11-0910
2026-11-1010
2026-11-1110
2026-11-1211
2026-11-1311
2026-11-1411

Who names it

Open roles naming Tool use, by company.

  • Attentive2
  • EvolutionIQ2
  • Clay1
  • ElevenLabs1
  • Headway1
  • Mirage (fka Captions)1
  • Patlytics1
  • Ramp1
  • Rogo1
  • Runway1
  • Sixfold1

Which roles

The same postings, by function and by seniority.

  • Engineering9
  • Product2
  • Research2
  • Mid8
  • Director2
  • Senior2
  • Staff/Principal1

Named alongside Tool use

Terms that appear in the same postings far more often than chance would put them there. The number is how many of the 11 companies pair the two.

Open roles naming Tool use

A sample from today’s data, New York roles first and one per company before any repeats. Links go to the employer’s own posting. For the full market, see AI jobs in NYC.

How this is counted

Every day we read the open roles on the public job boards of the New York AI companies in our coverage — the NYC AI 100 and the AI in NYC Show roster. This term is matched against each role’s description after removing the text a company repeats across its postings, so an “About us” paragraph cannot tag every role the company has open. A vendor’s own postings never count toward its own name.

The figure means named in a job posting. It does not mean used in production, and a “nice to have” counts the same as a requirement. Companies are the headline number because posting counts are dominated by whichever few employers are hiring hardest this month.

Full method, including the pay rules, is on the glossary index; the underlying series is the NYC AI Hiring Index.

Tool use: common questions

What does Tool use mean in an AI job posting?

Letting a language model call external functions and APIs — search, databases, code execution — by emitting structured requests the application then runs. Almost always appears next to AI agents and evals, in postings for engineers building agent platforms. It indicates hands-on agent work rather than chat-interface work. Expect design questions: how you would expose an internal API to a model, and how you would stop it being called in ways you did not intend.

How many New York AI companies are hiring for Tool use?

As of November 14, 2026, 11 of the 47 New York AI companies we track name Tool use in the description of at least one open role, across 13 postings (8 based in New York). The count refreshes daily from the companies’ own job boards.

What do roles that ask for Tool use pay in New York?

We do not publish a pay figure for Tool use yet. Fewer than eight New York postings naming it carry a distinct posted salary range, and below that number a median says more about two or three employers than about the market.

Which skills are asked for alongside Tool use?

In the same postings, the terms most distinctively paired with Tool use are Guardrails, Prompt engineering, Multimodal AI, Evals, Vector search. We rank pairings by how much more often they appear together than apart, so near-universal terms such as Python do not crowd out the informative ones.

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