Scholar Sidekick

Check Open Access

checkOpenAccess

Read-onlyIdempotent

Check whether a single scholarly work is openly accessible and where to find the best legal version. Use when the user asks 'is this open access?', 'where can I read this for free?', or wants the OA license/version before reusing or redistributing. Sourced from Unpaywall. Resolves DOI/PMID/PMCID/arXiv/ISBN/ADS inputs to a DOI before lookup; inputs that don't map to a DOI return doi=null and reason='no_doi'. arXiv inputs check the linked published-journal DOI when arXiv records one; a preprint without one returns doi=null and reason='no_doi' (Unpaywall does not index arXiv preprints, which are freely readable on arXiv regardless). Single identifier per call — does NOT accept comma/newline batches; loop one call per identifier for multiple papers. Returns: { doi, resolvedFrom?, reason?, result } where result has isOa (boolean), oaStatus ('gold' | 'green' | 'hybrid' | 'bronze' | 'closed'), title, bestLocation ({url, hostType: 'publisher' | 'repository', license, version: 'submittedVersion' | 'acceptedVersion' | 'publishedVersion'} or null), and locations (array of the same shape); result is null when no DOI could be resolved and reason explains why ('no_doi'). No sibling tool overlaps this — resolveIdentifier returns metadata but not OA status. Read-only and idempotent — safe to retry. Works anonymously against the public Scholar Sidekick API (rate-limited free tier); set SCHOLAR_API_KEY (a free ssk_ key from https://scholar-sidekick.com/account) for higher limits, or RAPIDAPI_KEY for paid RapidAPI tiers. Rate limits follow your tier; Unpaywall is queried server-side with its own caching.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`id`	Yes	A single scholarly identifier to check. 1–500 characters. Non-DOI inputs are resolved to a DOI server-side before the lookup; if no DOI can be derived, the tool returns doi=null with reason='no_doi'. Pass exactly one identifier — comma/newline batches are NOT accepted by this tool; loop one call per identifier for multiple papers. Accepted: DOI, PMID, PMCID, arXiv ID, ISBN, or NASA ADS bibcode (with or without prefixes).

Output Schema

TableJSON Schema

Name	Required	Description
`doi`	Yes
`reason`	No
`result`	Yes	Open-access status, or null when no DOI resolved.
`resolvedFrom`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedJun 4, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Goes well beyond the annotations by explaining DOI resolution behavior, doi=null/no_doi cases, arXiv preprint semantics, idempotence, server-side Unpaywall caching, and API tier/rate-limit behavior. It also clarifies that the tool is read-only and safe to retry, reinforcing the annotations.

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?

The description is long but every section earns its place: purpose, trigger queries, input rules, edge cases, return shape, sibling differentiation, and authentication/rate limits. It is front-loaded with the core purpose before diving into implementation details, though some phrasing could be tightened.

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

Completeness5/5

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

Given the tool's one parameter, rich output schema, and annotations, this description is fully complete for an agent to select and invoke it correctly. It covers input constraints, edge cases, return shape, error-like behavior, authentication needs, rate limits, and relationship to sibling tools.

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

Parameters4/5

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

The input schema already covers the id parameter thoroughly, so the baseline is 3. The description adds value beyond the schema with the arXiv edge case: arXiv inputs check the linked published-journal DOI, and preprints without one return no_doi because Unpaywall does not index arXiv separately. It also reinforces the single-identifier and looping behavior.

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?

Description names a specific verb and resource: 'Check whether a single scholarly work is openly accessible and where to find the best legal version.' It clearly distinguishes itself from siblings by explicitly stating that no sibling tool overlaps it and that resolveIdentifier does not provide OA status.

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

Usage Guidelines5/5

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

Provides explicit when-to-use triggers: exact user phrasings like 'is this open access?' and 'where can I read this for free?', as well as reuse/license scenarios. It also names the closest sibling, resolveIdentifier, and explains why it is not an alternative for this task.

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

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