PMC (PubMed Central)

PMC is a full-text archive of biomedical and life sciences articles. It is separate from PubMed -- PubMed has citations/abstracts, PMC has full text. Not all PubMed articles are in PMC, and vice versa.

E-utilities for PMC

Base URL

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/

Same E-utilities as PubMed, but with db=pmc.

eSearch -- Search PMC

GET /esearch.fcgi?db=pmc&term={query}&retmode=json

Same parameters as PubMed eSearch. Returns PMC UIDs (numeric, e.g., 13033346). You need to prepend "PMC" to get a PMCID (e.g., PMC13033346).

eFetch -- Get Full Text XML

GET /efetch.fcgi?db=pmc&id={pmcid}&retmode=xml

rettype	retmode	Returns
(omit)	`xml`	JATS XML -- full text only for open-access articles; metadata only otherwise, with no error. See the hazard below before using this.
`medline`	`text`	MEDLINE format

Example:

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pmc&id=7029759&retmode=xml

The XML uses JATS (Journal Article Tag Suite) format:

<front> -- journal metadata, article metadata, author info
<body> -- full article text with <sec> sections, <p> paragraphs, <fig> figures
<back> -- <ref-list> with all references

Pass numeric IDs only (not "PMC7029759", just "7029759").

Hazard: eFetch returns metadata-only XML for non-OA articles, with HTTP 200

This is the most dangerous failure in this skill, because nothing about the response says it failed. When the publisher does not permit XML redistribution, eFetch returns a well-formed <pmc-articleset> containing <front> metadata, no <body>, and the reason as an XML comment -- which every standard parser discards. Verified 2026-07-27 on PMCID 1500000:

HTTP/1.1 200 OK

<pmc-articleset><article article-type="obituary" ...>
  <!--The publisher of this article does not allow downloading of the full text in XML form.-->
  <front>...</front>
</article></pmc-articleset>

An agent that fetches this, parses it, and reports "retrieved full text" has retrieved only the title, journal, and author list. This is the common case, not an edge case: full text via eFetch is limited to roughly the 3M-article PMC Open Access Subset, while PMC holds ~10M — so most PMCIDs you hand to eFetch come back without a body.

Always confirm <body> exists before claiming you have full text. Three ways, in order of preference:

Check availability first with the PMC OA Web Service (below). It tells you whether a package exists before you spend the fetch.
Use scripts/jats_to_text.py, which exits non-zero with no <body> element when the article is metadata-only and surfaces the publisher-restriction comment instead of dropping it.
Fall back to Europe PMC (references/europepmc.md), whose fullTextXML endpoint returns a clean 404 for the same article rather than a 200 with no body -- an honest failure is easier to handle than a plausible one.

If full text is unavailable, say so explicitly and offer the abstract (PubMed eFetch) or an OA copy elsewhere (Unpaywall, CORE) rather than presenting <front> metadata as the article.

PMC OA Web Service -- is full text actually available?

Not the same thing as the ID Converter: this answers "does a downloadable full-text package exist for this PMCID", which is exactly what the eFetch hazard above requires you to know in advance.

GET https://www.ncbi.nlm.nih.gov/pmc/utils/oa/oa.fcgi?id={pmcid}

Returns XML (no JSON option). Verified 2026-07-27:

xml

<OA><records returned-count="1" total-count="1">
  <record id="PMC7029759" citation="F1000Res. 2020 Feb 7; 9:72" license="CC BY" retracted="no">
    <link format="tgz" updated="2024-04-23 12:25:15"
          href="ftp://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_package/e5/c9/PMC7029759.tar.gz"/>
  </record>
</records></OA>

Distinguish the two failure codes -- they mean different things and both arrive with HTTP 200:

Response	Meaning
`<records>` with a `<record>` and `<link>`	In the OA Subset; full text is retrievable
`<error code="idIsNotOpenAccess">`	The article exists but is not in the OA Subset -- eFetch will return metadata only. This is the case to route to Europe PMC or Unpaywall.
`<error code="idDoesNotExist">`	No such PMCID. A bad identifier, not a coverage gap -- re-check the format or convert via the ID Converter.

Per-record attributes worth reading:

Attribute	Why it matters
`license`	The actual reuse terms (`CC BY`, `CC BY-NC`, ...). Report these when you quote or redistribute text.
`retracted`	`"no"` or `"yes"`. Summarizing a retracted paper as current evidence is a correctness failure, not a formatting one -- check it before quoting.
`citation`	Human-readable citation string, handy for provenance.

format values are tgz (article XML plus figures) and sometimes pdf. The href is an FTP URL, and swapping the scheme to HTTPS does not work -- https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_package/... returns 404 (verified 2026-07-27). Use the FTP URL as given, or get the same XML over HTTPS from eFetch / Europe PMC fullTextXML once this service has confirmed the article is in the subset.

BioC API -- Structured Full Text

An alternative way to get full text in a structured passage format.

Base URL

https://www.ncbi.nlm.nih.gov/research/bionlp/RESTful/pmcoa.cgi/

Endpoint

GET /BioC_{format}/{id}/{encoding}

Parameter	Values
`format`	`json` or `xml`
`id`	PMID (e.g., `17299597`) or PMCID (e.g., `PMC7029759`)
`encoding`	`unicode` or `ascii`

Example:

https://www.ncbi.nlm.nih.gov/research/bionlp/RESTful/pmcoa.cgi/BioC_json/PMC7029759/unicode

Response structure (JSON):

json

{
  "source": "PMC",
  "documents": [{
    "id": "PMC7029759",
    "infons": {"license": "...", "doi": "..."},
    "passages": [
      {
        "offset": 0,
        "infons": {"section_type": "TITLE"},
        "text": "Article title..."
      },
      {
        "offset": 42,
        "infons": {"section_type": "ABSTRACT"},
        "text": "Abstract text..."
      },
      {
        "offset": 500,
        "infons": {"section_type": "INTRO"},
        "text": "Introduction text..."
      }
    ]
  }]
}

Section types: TITLE, ABSTRACT, INTRO, METHODS, RESULTS, DISCUSS, CONCL, REF, SUPPL, FIG, TABLE

Coverage: ~3 million articles from the PMC Open Access Subset.

PMC ID Converter API

Converts between PMID, PMCID, DOI, and Manuscript ID.

Base URL

https://pmc.ncbi.nlm.nih.gov/tools/idconv/api/v1/articles/

Parameters

Parameter	Required	Description
`ids`	Yes	Up to 200 comma-separated IDs
`idtype`	No	`pmcid`, `pmid`, `mid`, `doi` (default: auto-detect)
`format`	No	`json`, `xml`, `csv` (default: xml)
`tool`	Recommended	Your application name
`email`	Recommended	Your contact email

Example:

https://pmc.ncbi.nlm.nih.gov/tools/idconv/api/v1/articles/?ids=PMC7029759&format=json

Response:

json

{
  "status": "ok",
  "records": [{
    "pmcid": "PMC7029759",
    "pmid": "32117569",
    "doi": "10.12688/f1000research.22211.2"
  }]
}

Only returns results for articles that are in PMC. If an article is in PubMed but not PMC, no PMCID will be returned.

Rate Limits

Service	Limit
E-utilities (`db=pmc`)	3/sec without key, 10/sec with key
BioC API	Follow general NCBI policy (3/sec without key)
ID Converter	Follow general NCBI policy

Include tool and email parameters on E-utility requests. Large batch jobs should run outside peak hours (Mon-Fri 5AM-9PM ET).