How does the 200K context window change agent design?

Claude accepts up to 200K tokens of combined input in a single request, so an agent can reason over an entire contract, codebase, or research paper without chunking or building a retrieval pipeline. Counting tokens first confirms the payload fits before any generation cost is incurred.

Can an agent estimate cost before spending model compute?

Yes. The count_tokens operation, available on both APIs, accepts the same messages and system prompt shape as a real request and returns an exact token count without consuming model compute. Agents use it to stay within budgets, choose between model tiers, and decide whether to truncate retrieved content.

Anthropic APIs for AI Agents

AI/MLLanguage ModelsJentic-Generated SpecsAPI keyAgent Ready

www.anthropic.com·Developer portal → docs.anthropic.com

Anthropic API Catalog

2 APIs across 1 product group. All share one credential.

AI/ML2

Anthropic APISend prompts to Claude models for text generation, reasoning, and code tasks.~11 endpoints Anthropic Messages APISend messages to Claude for reasoning, code, and analysis tasks; count tokens before dispatch to manage cost and context.~2 endpoints

Which Anthropic API should I use?

I want to...	Use	Why
Synchronous chat completions with tool use and streaming	Anthropic Messages API	A focused two-endpoint surface for POST /messages and token counting, ideal when the agent only delegates reasoning steps to Claude and does not need batch or model-management operations.
Bulk async processing, batch management, and model discovery	Anthropic API	The broader 11-endpoint surface adds message batches, batch status and result retrieval, batch cancellation, and model listing on top of the same messaging and token-counting operations.
Counting tokens before a request to estimate cost	Anthropic Messages API	Both APIs expose count_tokens; the Messages API is the lighter choice when token counting and single completions are all the agent needs.

Install Jentic One Beta

Connect the Anthropic APIs to your agent

Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Anthropic APIs, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.

Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.

Step 1: Jentic One Host machine

# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fanthropic.com" | sh

Step 2: Agent machine

# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fanthropic.com" | sh
jentic register       # connects your agent to your Jentic One instance

Jentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.

Once connected, ask your agent something like: .

Why Jentic?

What agents get from Jentic-routed access to this vendor.

Setup

Calling these APIs by hand means setting the x-api-key and anthropic-version headers on every request and tracking batch job ids yourself. With Jentic One you install once, add the Anthropic APIs from the Jentic directory, store the API key once, and your agent calls any operation across both surfaces.

Permission scoping

Because you run Jentic One yourself, your own rules decide which Anthropic operations the agent may call. You can scope it to sending messages and counting tokens while leaving out batch creation, batch cancellation, or model listing, and an operation with no granting rule cannot be invoked.

Credential isolation

Your Anthropic API key is stored once, encrypted, by your own Jentic One instance and injected with the required version header at execution time. It never enters the agent's prompt, logs, or context.

FAQs

Specific to using Anthropic APIs through Jentic.

What can an agent do across Anthropic's APIs?

An agent can send prompts to Claude for reasoning, code, and analysis, run multi-step tool-use loops, count tokens to control cost, submit and monitor asynchronous message batches, and list available Claude models to choose the right one. The messaging and token-counting operations appear on both surfaces, while batch and model-management operations live on the broader Anthropic API.

Why does Jentic publish these specs?

Anthropic does not publish an OpenAPI specification. Jentic generates and maintains these specs so agents and developers can call Claude through structured tooling. They are validated against the live API and kept up to date across the messaging, batch, token-counting, and model endpoints.

Does one credential work across both APIs?

Yes. Both the Messages API and the broader Anthropic API authenticate with the same Anthropic API key in the x-api-key header, paired with the required anthropic-version header. A single stored credential covers every operation on both surfaces.

Which API should an agent use for synchronous chat versus bulk work?

Use the Messages API for real-time completions, streaming, and tool-use loops when a small two-endpoint surface is enough. Use the broader Anthropic API when the agent also needs message batches for high-volume async work, batch result retrieval or cancellation, or model listing.

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For Agents

APIs2 in catalogue

Endpoints13 indexed

AuthAPI key — 1 credential for all 2 APIs

ProvenanceJentic-generated specs

An agent can send prompts to Claude models for reasoning, code, and long-document analysis, run tool-use loops, count tokens before dispatch to control cost, and submit or monitor asynchronous message batches for bulk workloads. It can also list available Claude models and inspect their context limits before choosing which one to call.

Anthropic pairs Claude's long-context reasoning with a small, message-centric API surface: the same endpoint handles single-shot completions, streaming, and multi-step tool-use agent loops. Its 200K-token context window lets an agent reason over an entire document in one request instead of building a retrieval pipeline, and a dedicated token-count endpoint lets the agent estimate cost before it spends any model compute.

Use for: Sending prompts to Claude for text generation, reasoning, code, and long-document analysis, running tool-use loops, counting tokens before dispatch, and submitting or monitoring asynchronous message batches.

Not supported: image generation, audio transcription, text embeddings, vector storage, model fine-tuning

Credentials: Both APIs use the same Anthropic API key in the x-api-key header plus a required anthropic-version header, so one credential covers every operation across both surfaces.

What AI Agents Can Do with Anthropic

Each workflow spans multiple Anthropic APIs. Jentic routes each operation to the right API automatically.

Size a prompt, then send it to Claude

Before dispatching a request, the agent counts tokens for the intended messages and system prompt, confirms the payload fits the chosen model's context window, and only then sends the completion. This keeps requests inside budget and context limits without wasting model compute on oversized inputs.

Example prompt:

Call count_tokens with the candidate messages and system prompt; if the count is under the model limit, call the messages endpoint with the same payload and model claude-sonnet

APIs used

Anthropic Messages API + Anthropic API

Interactive reasoning with a batch fallback

The agent handles real-time questions through synchronous message completions, then hands large offline workloads to the batch surface so hundreds of requests run asynchronously at reduced cost. It polls batch status and retrieves results once processing finishes.

Example prompt:

Answer live questions via POST /messages, then create a message batch with the day's bulk requests, poll batch status until complete, and download the results

APIs used

Anthropic Messages API + Anthropic API

Pick a model, then run a tool-use loop

The agent lists available Claude models to choose one that fits the task and context requirement, then drives a tool-use loop against the messages endpoint: Claude returns tool_use blocks, the runtime executes each tool, and the appended history is posted back for the next turn.

Example prompt:

Call GET /v1/models to select a model, then POST /messages with tool definitions, parse the tool_use block, execute the tool, and POST /messages again with the tool_result appended

APIs used

Anthropic API + Anthropic Messages API

Anthropic APIs for AI Agents

Anthropic API Catalog

AI/ML2

Which Anthropic API should I use?

Connect the Anthropic APIs to your agent

Why Jentic?

FAQs

Start Connecting APIs to Your AI Agents

What AI Agents Can Do with Anthropic

If you need a different AI/ML vendor