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

Annotations only say readOnly/openWorld; the description adds information the annotations cannot convey: it is a public REST API needing no key, abstracts are excluded from results, and each successful call costs $0.002 USDC via x402 on Base/Solana/Arc while failed calls are free. That payment mechanic is decisive behavioral context an agent must have before invoking.

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?

Front-loaded with the capability, returned fields, and scope caveat before the sibling-routing and pricing sentences, so an agent gets the essentials first. It is dense but nearly every clause carries new information; only the 'Related tools on this server, for a different need' framing is slightly padded.

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 two-parameter search tool with a full output schema, annotations, and 100% schema coverage, the description covers what it returns, what it excludes, cost/auth model, and alternatives. Nothing an agent needs in order to call it correctly is missing.

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?

Schema coverage is 100%, with 'q' documented as search words or Europe PMC query syntax (1-200 chars) and 'limit' as 1-25 defaulting to 5. The description adds nothing about parameter syntax, so the schema does all the work — the baseline 3 applies.

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?

States a specific verb+resource ('Europe PMC literature search') and immediately enumerates the returned fields (PMID/source id, title, authors, journal, year, DOI, cited-by count, link) plus the scope ('life-science papers including preprints; abstracts are not included'). It also names two sibling tools it is not, so an agent can route without opening schemas.

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?

Gives explicit when-to-use conditions for two alternatives ('search_dev_to_articles when you need DEV Community latest articles for one tag', 'search_emedicine_articles when you need Medscape eMedicine clinical articles by specialty'). However, the closest competitor in the sibling list, search_pubmed_article_metadata (plus search_crossref, search_unpaywall, search_datacite), is never mentioned, leaving the most likely ambiguity unresolved.

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