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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context the annotations cannot convey: the rate/allowance model and the x402 per-call charge, which is important for an agent deciding whether to invoke it repeatedly.

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?

Two short sentences, both earning their place: the first enumerates the payload, the second covers the cost model. Front-loaded and free of filler, though the field list is somewhat list-heavy.

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?

With an output schema present, return values need not be explained again, and the pricing disclosure covers the main non-obvious behavior. The missing piece is routing guidance versus sibling tools (crossref__search, crossref__journal), which is the only meaningful gap for a one-parameter lookup.

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?

There is a single required parameter and schema description coverage is 100%, so the schema does all the work. The description adds no format or normalization guidance for the DOI beyond what the schema states, which is the expected baseline here.

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 names the resource (DOI metadata) and enumerates the returned fields (title, authors, journal, dates, references count, licence), so the agent knows exactly what a call yields. It is specific but does not explicitly differentiate itself from siblings like crossref__search or crossref__journal, which matters given the crowded scholarly-tool namespace.

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?

There is no statement of when to use this tool versus crossref__search (query-based lookup) or the other crossref__* endpoints. The only guidance given is commercial (free tier, then $0.002 via x402), which tells the agent about cost but not about selection.

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