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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior, so safety is covered. The description adds genuinely new operational context the annotations lack: a free daily allowance and a $0.002 USDC x402 charge after it, which matters for call budgeting. It doesn't note result limits or pagination, keeping it short of a 5.

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: the capability is front-loaded and the cost model follows. Every clause earns its place, with no boilerplate or restatement of the title.

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 single-parameter lookup with an output schema already present, the description covers capability, return content, and cost. Only minor gaps remain — result limits, pagination, and how name matching works — which are low-stakes here.

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?

Only one parameter exists and schema coverage is 100% ('q: Funder'), so the schema already carries the load. The description's 'by name' adds a small hint that q is a name-based query rather than an ID lookup, but nothing about matching behavior or expected input format. Baseline 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 gives a specific verb+resource ('Research funders') and states the return content ('with Funder Registry ids'), which clearly distinguishes it from crossref__members, crossref__journal, and crossref__search as a funder-lookup tool. It stops short of naming or contrasting those siblings explicitly, so it lands at 4 rather than 5.

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?

The description says what it is but never says when to reach for it over the other crossref or ror__search tools, nor does it state any prerequisites (e.g., that 'q' must be a funder name rather than a DOI or member). Usage is only inferable from the tool name and resource.

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