Get Paper PDF URL

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

The description adds behavioral details beyond annotations: it explains the source priority order, what the returned JSON contains (pdf_url, source, title, year, browser_excerpt), and that errors are returned as strings. Annotations already indicate read-only, idempotent, and open-world behavior, so the description complements well without contradiction.

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

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

The description is concise with three main sections: purpose, source priority, and return format. It front-loads the core purpose and avoids unnecessary details. Minor redundancy exists in describing the return format twice (JSON fields and str type), but overall it is efficient and well-structured.

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

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

For a simple tool with one parameter and a clear output, the description covers the key aspects: input, processing logic (source priority), and output format. It also notes the possibility of browser_excerpt in fallback. It is thorough enough for an agent to use effectively, though could have mentioned what happens when no PDF is found beyond returning an error.

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

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

The input schema covers 100% of parameters with descriptions (paper_title). The description restates the parameter structure but adds no new semantic meaning beyond what the schema provides. Given high schema coverage, a score of 3 is appropriate.

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

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

The description clearly states the tool's purpose: 'Find the best open-access PDF URL for a paper by title.' It specifies the action (find best PDF URL) and the resource (paper by title). This distinguishes it from sibling tools like paper_get_fulltext or paper_get_metadata, which serve different purposes.

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

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

While the description provides a source priority chain (Semantic Scholar OA → arXiv PDF → Unpaywall → gomcp browser), it does not explicitly state when to use this tool versus its siblings. The usage context is implied by the tool's name and purpose, but explicit guidance on edge cases (e.g., when to prefer other tools) is missing.

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