Paper Full Text Retrieval (by arXiv ID, DOI, PMID, or PMCID)

{
  "type": "object",
  "anyOf": [
    {
      "required": [
        "id"
      ]
    },
    {
      "required": [
        "doi"
      ]
    }
  ],
  "properties": {
    "id": {
      "type": "string",
      "description": "arXiv id, DOI, OpenAlex id, PMID, or PMCID"
    },
    "doi": {
      "type": "string",
      "description": "alias for id (DOI form)"
    }
  },
  "additionalProperties": false
}

{
  "type": "object",
  "properties": {
    "code": {
      "type": "string",
      "description": "Present only on the error case instead of `count`/`items` -- e.g. 'HTTP_400' for a bogus/unmatched DOI. Other values are not documented."
    },
    "count": {
      "type": "number",
      "description": "Number of entries in `items` (typically 1)."
    },
    "items": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "text": {
            "type": "string",
            "description": "The full paper body as a single concatenated plain-text string."
          },
          "type": {
            "type": "string",
            "description": "Typically the literal string 'paper_fulltext'."
          },
          "query": {
            "type": "string",
            "description": "Echoes the requested `id`/`doi` input value."
          },
          "arxivId": {
            "type": "string",
            "description": "The arXiv identifier for the paper, present for arXiv papers. Whether an equivalent id field is present for a DOI/PMID/PMCID lookup served by Europe PMC or OpenAlex instead of arXiv is not documented."
          },
          "sections": {
            "type": "array",
            "items": {
              "type": "object",
              "properties": {
                "text": {
                  "type": "string"
                },
                "heading": {
                  "type": "string"
                }
              },
              "additionalProperties": true
            },
            "description": "The paper's body split into named sections, in document order."
          },
          "openAccess": {
            "type": "boolean"
          },
          "fulltextSource": {
            "type": "string",
            "description": "Which source served the full text, e.g. 'ar5iv' for an arXiv paper; the provider's own documentation additionally names Europe PMC for biomedical identifiers and OpenAlex-located open-access copies for others, but neither has been observed in testing."
          }
        },
        "additionalProperties": true
      },
      "description": "Present on a successful lookup; absent on the error case (see `code`/`message`)."
    },
    "message": {
      "type": "string",
      "description": "Present only on the error case, alongside `code`; a short human-readable reason."
    }
  },
  "description": "The paper lookup result.",
  "additionalProperties": true
}