> ## Documentation Index
> Fetch the complete documentation index at: https://docs.consensus.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Pricing, rate limits and data privacy

> Pricing, rate limits, interfaces and data use compared across the Consensus API, PubMed E-utilities, Europe PMC, OpenAlex, Semantic Scholar and Crossref, including what each provider does with your queries.

## Pricing

| | Free usage | Paid options |
| - | - | - |
| **Consensus** | <ul><li>30 calls a month</li><li>Up to 20 papers per request</li></ul> | <ul><li>Pro and Teams: 500 calls a month</li><li>Deep: 2,000 calls a month</li><li>\$0.05 per extra call, up to your plan's maximum</li><li>Enterprise: custom volumes</li></ul> |
| **PubMed** | <ul><li>Free<sup>[1](#source-1)</sup></li></ul> | <ul><li>—</li></ul> |
| **Europe PMC** | <ul><li>Free<sup>[2](#source-2)</sup></li></ul> | <ul><li>—</li></ul> |
| **OpenAlex** | <ul><li>\$1 of API usage a day with a free key</li><li>A keyword search costs \$1 per 1,000 calls<sup>[3](#source-3)</sup></li></ul> | <ul><li>Prepaid usage</li><li>Annual plans from \$5,000 a year<sup>[4](#source-4)</sup></li></ul> |
| **Semantic Scholar** | <ul><li>Unauthenticated access</li><li>A free API key on request<sup>[5](#source-5)</sup></li></ul> | <ul><li>No published price</li></ul> |
| **Crossref** | <ul><li>Free public API, no sign-up<sup>[6](#source-6)</sup></li></ul> | <ul><li>Metadata Plus subscription<sup>[7](#source-7)</sup></li></ul> |

A dash (—) means we didn't find a paid option in that provider's documentation as of November 2026.

### How Consensus counts calls

* One call covers up to 100 papers returned, rounded up, with a minimum of one call per request. A request for 20 papers is 1 call. A request for 150 papers is 2 calls.
* The API and the MCP server share one monthly pool.
* Usage resets on the 1st of each month.

See [plans and access](https://docs.consensus.app/api-plans-and-access.md) for page sizes and features by plan.

## Rate limits

| | Without a key | With a key or plan |
| - | - | - |
| **Consensus** | <ul><li>A key is required</li></ul> | <ul><li>1 request a second on self-serve plans</li><li>Thread polling: 3 a second</li><li>Enterprise: custom</li></ul> |
| **PubMed** | <ul><li>3 requests a second<sup>[8](#source-8)</sup></li></ul> | <ul><li>10 a second with a free key</li><li>Higher on request<sup>[8](#source-8)</sup></li></ul> |
| **Europe PMC** | <ul><li>10 requests a second (500 a minute) per IP<sup>[9](#source-9)</sup></li></ul> | <ul><li>No key needed</li></ul> |
| **OpenAlex** | <ul><li>10 requests a second</li><li>A shared daily budget per IP<sup>[4](#source-4)</sup></li></ul> | <ul><li>30 a second with a free key</li><li>50 on an annual plan</li><li>Semantic search: 1 a second<sup>[10](#source-10)</sup></li></ul> |
| **Semantic Scholar** | <ul><li>A pool of 1,000 requests a second shared by all unauthenticated users</li><li>May be throttled under heavy use<sup>[5](#source-5)</sup></li></ul> | <ul><li>1 a second with a new key<sup>[5](#source-5)</sup></li></ul> |
| **Crossref** | <ul><li>Public pool: 5 a second</li><li>Polite pool, with your email: 10 a second<sup>[7](#source-7)</sup></li></ul> | <ul><li>Metadata Plus: 150 a second<sup>[7](#source-7)</sup></li></ul> |

## Interfaces and code samples

| | Interfaces |
| - | - |
| **Consensus** | <ul><li>REST, with samples in cURL, Python, JavaScript, Go, PHP, Ruby and Java</li><li>[MCP server](https://docs.consensus.app/consensus-mcp.md) for assistants and AI agents</li></ul> |
| **PubMed** | <ul><li>URL-based REST interface (E-utilities)<sup>[8](#source-8)</sup></li></ul> |
| **Europe PMC** | <ul><li>REST, SOAP, OAI-PMH and bulk FTP<sup>[11](#source-11)</sup></li></ul> |
| **OpenAlex** | <ul><li>REST, OQL and a CLI</li><li>Connectors for Claude and ChatGPT<sup>[12](#source-12)</sup></li><li>A full snapshot of the database<sup>[4](#source-4)</sup></li></ul> |
| **Semantic Scholar** | <ul><li>REST</li><li>Downloadable datasets<sup>[5](#source-5)</sup></li></ul> |
| **Crossref** | <ul><li>REST and content negotiation<sup>[6](#source-6)</sup></li><li>An annual public data file<sup>[13](#source-13)</sup></li></ul> |

## Data privacy: what happens to your queries

What you search for can reveal your pipeline: drug targets, materials, competitor products. Check what a provider does with your queries before you send them.

### Consensus

* **SOC 2 Type II** compliant, hosted on Google Cloud.
* **Customer data isn't used to train AI models.** The LLM providers Consensus uses keep no data from requests.
* **Zero data retention** and a **data-processing agreement** are available on Enterprise contracts.
* API keys are shown once, and can be named, revoked and rotated from the dashboard.

See [Security and data handling](https://docs.consensus.app/enterprise/security.md) for encryption, infrastructure and access controls.

### Other providers

The free APIs publish data licences and usage terms rather than enterprise privacy commitments:

* **PubMed** asks every caller to identify themselves with `tool` and `email` parameters<sup>[8](#source-8)</sup>.
* **Europe PMC** serves open-access content and metadata, and doesn't allow automated bulk download of other content<sup>[11](#source-11)</sup>.
* **OpenAlex** releases all its data under CC0. API keys are tied to an account<sup>[4](#source-4)</sup>.
* **Semantic Scholar**'s licence says AI2 uses the data you send to call the API "for the purpose of providing and improving the API". Its data is licensed CC BY-NC or ODC-BY, and attribution is required<sup>[14](#source-14)</sup>.
* **Crossref** asks for an email in the polite pool. Most of its metadata isn't subject to copyright<sup>[6](#source-6)</sup>.

Read each provider's terms against your own policy.

## Related

> [card] [API plans and access](https://docs.consensus.app/api-plans-and-access.md)
>
> Calls, page sizes, features and errors by plan.

> [card] [Compare scholarly APIs](https://docs.consensus.app/api-comparison)
>
> Why teams choose Consensus, and every API at a glance.

## Sources

Facts about other providers were checked against their official documentation on 5 November 2026. Limits and prices change, so check the source before you build on a number.

1. [About PubMed](https://pubmed.ncbi.nlm.nih.gov/about/): "more than 40 million citations and abstracts of biomedical literature"; "does not include full text journal articles"; a free resource.
2. [About Europe PMC](https://europepmc.org/About): 49.2 million abstracts and 12.5 million full-text articles; searches abstracts and full text; searches can be limited to clinical trials, preprints or article sections such as Methods; free to anyone.
3. [OpenAlex example costs](https://help.openalex.org/access/example-costs/): search costs \$1 per 1,000 calls; content downloads cost \$10 per 1,000.
4. [OpenAlex pricing](https://help.openalex.org/access/pricing/): all data CC0; \$1 of free API usage a day with a key; annual plans from \$5,000 a year; the whole database can be downloaded as a snapshot refreshed every quarter. A keyless response notes that it shares a \$0.10 daily budget per IP address.
5. [Semantic Scholar API overview](https://www.semanticscholar.org/product/api): 214 million papers; unauthenticated requests share 1,000 requests a second across all users and may be throttled under heavy use; the introductory limit for an API key is 1 request a second. The API also serves SPECTER2 embeddings and a Recommendations service for similar papers.
6. [Crossref REST API](https://www.crossref.org/documentation/retrieve-metadata/rest-api/): bibliographic metadata including funding, licence and abstracts; no sign-up required; most metadata isn't subject to copyright.
7. [Crossref access and authentication](https://www.crossref.org/documentation/retrieve-metadata/rest-api/access-and-authentication/): public pool 5 requests a second, polite pool 10, Metadata Plus 150.
8. [A General Introduction to the E-utilities](https://www.ncbi.nlm.nih.gov/books/NBK25497/): more than 3 requests a second without an API key returns an error; with a key, up to 10 a second by default; higher rates by request. Requests without registered `tool` and `email` values may be blocked.
9. Europe PMC team on the [Europe PMC web services forum](https://groups.google.com/a/ebi.ac.uk/g/epmc-webservices/c/x3PLL09mels), 1 October 2024: the rate limit is 10 requests a second (500 a minute), and no API key is required.
10. [OpenAlex authentication and rate limits](https://help.openalex.org/api/authentication/): 10 requests a second with no key, 30 with a free key or prepaid usage, 50 on an annual plan; semantic search is limited to 1 a second.
11. [Europe PMC developer resources](https://europepmc.org/developers): REST, SOAP, OAI-PMH and FTP access to open-access content and metadata; automated bulk download of other content isn't allowed. The [Articles RESTful API](https://europepmc.org/RestfulWebService) includes `/{id}/fullTextXML`.
12. [OpenAlex help center index](https://help.openalex.org/llms.txt): REST URLs, OQL, a CLI, and Claude and ChatGPT connectors.
13. [Tips for using the Crossref REST API](https://www.crossref.org/documentation/retrieve-metadata/rest-api/tips-for-using-the-crossref-rest-api/): annual public data file.
14. [Semantic Scholar API License Agreement](https://www.semanticscholar.org/product/api/license): AI2 uses the data you send to call the API "for the purpose of providing and improving the API"; data is licensed CC BY-NC or ODC-BY; attribution required.


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