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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=true), so the bar is lower. The description adds genuinely useful non-annotation context: the call costs $0.002 USDC under the x402 payment scheme, which an agent must know before invoking. It stops short of describing failure behavior for unresolvable DOIs/URLs or how the external fetch affects latency.

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 tight sentences, front-loaded with the capability and the input/output surface, with pricing immediately after. Slightly promotional phrasing ('a ready reference') costs a little density, but nothing is wasted.

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 no output schema, the description should clarify what comes back (a formatted citation string, and whether internal links/DOIs are included), and it should resolve the mutual-exclusivity of the three identifier inputs. For a paid tool with four loosely-specified parameters, those omissions leave real gaps.

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 description coverage is only 25% (just the 'style' parameter), which the description partially compensates for by listing the styles and naming the three identifier types. But with zero required parameters, the critical semantics — that doi/url/isbn are alternatives and presumably exactly one must be supplied — are never stated in either place.

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 (format/generate) and resource (citation) and enumerates the output styles (APA, MLA, Chicago, Harvard, IEEE, Vancouver, BibTeX) plus the accepted inputs (DOI, ISBN, URL). However, it never distinguishes itself from the close sibling 'citecheck', leaving the agent to guess which one handles citation formatting vs. citation validation.

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?

Usage is only implied: if you have a DOI, ISBN or URL and want a formatted reference, use this. There is no explicit when-to-use statement, no mention of the 'citecheck' alternative, and no guidance on what to do when an identifier is invalid or unresolvable.

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