Research Paper & DOI Lookup (Crossref)

paper_lookup

Verify a citation or DOI, or find research papers on a topic. Searches Crossref (150M+ records) by DOI, keywords, author or title with year and type filters: title, authors with ORCID, journal or publisher, date, type, ISSN/ISBN, citation and reference counts, licence, full-text links and funders. Abstracts are excluded. Use when an agent must check that a reference exists and is cited correctly. $0.005 per call, USDC on Base (x402).

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "paper_lookup"
  }
}

Input Schema

Name	Required	Description
`doi`	No	DOI to resolve, e.g. 10.1038/nature12373
`type`	No	Crossref type, e.g. journal-article, book-chapter, posted-content
`limit`	No	Results 1-20 (default 10)
`query`	No	Keywords (title, abstract words, topics)
`author`	No	Author name filter
`from_year`	No	Earliest publication year
`until_year`	No	Latest publication year
`payment_signature`	No	x402 v2 PAYMENT-SIGNATURE header value. Omit to receive payment requirements.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 16, 2026

TDQS

A4.1/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and does well: it names the upstream source, discloses that abstracts are excluded, lists the returned metadata fields, and surfaces the cost model ($0.005 per call, USDC on Base via x402). It does not mention rate limits, timeout/error behavior, or whether results are cached, so it is strong but not exhaustive for a paid network call.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose and usage trigger are front-loaded in the first two sentences, and the cost/payment note is correctly placed at the end. The long run-on enumeration of returned fields is dense and could be trimmed since there is no output schema, but little is genuinely wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an eight-parameter tool with no annotations and no output schema, the description compensates by specifying the data source, the returned metadata shape, the abstract exclusion, and the payment requirement. The main residual gap is operational behavior under failure or rate limiting, which an agent paying per call would want to know.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the eight parameters are already fully documented in the schema and the baseline of 3 applies. The description adds only high-level framing (search by DOI, keywords, author or title, with year and type filters) and spends most of its parameter-adjacent words on return fields rather than input semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States two concrete verb+resource pairs up front: verifying a citation/DOI and finding papers on a topic, backed by the named data source (Crossref, 150M+ records) and the lookup keys (DOI, keywords, author, title). An agent can immediately tell this is a scholarly-record lookup tool and not something else.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Use when an agent must check that a reference exists and is cited correctly" gives an explicit trigger, and the DOI-vs-keywords framing implicitly separates the verification mode from the discovery mode. It stops short of stating when not to use it or which of the two modes to prefer when both could apply.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Research Paper & DOI Lookup (Crossref) tools Inspect

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