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

Annotations cover readOnly/idempotent/openWorld, so the description is freed to disclose what annotations cannot: per-call request budget (max 20 Datatracker requests), retry-inclusive accounting, exact per-id request costs, partial-failure semantics ('failed with reason request_limit'), and 'Unknown ids return found: false.' These are genuinely useful operational details. It stops short of 5 only because pagination/ordering of results across a batch isn't fully spelled out.

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 front-loaded correctly with the core purpose, but the middle sentence is a run-on enumeration of accepted formats that could be trimmed, and the final sentence on request accounting is dense. It earns its length given the tool's complexity, but structure is somewhat heavy for a one-parameter tool.

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?

Given a single parameter, full schema coverage, and an output schema, the description supplies the operational context an agent needs: batch limit, accepted input forms, partial-failure behavior, and per-type return shapes. It's complete enough to invoke correctly, with only minor gaps in cross-batch result ordering.

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%, so the baseline is 3. The description adds value by enumerating accepted identifier forms (bare number, 'RFC 9110', 'rfc9110', draft with/without revision, 'BCP 14', file name, URLs on specific hosts) and the 10-item batch cap, but this largely duplicates the schema's own item description. Marginal lift above baseline.

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 opens with a precise verb+resource+scope: 'Get the current status of up to 10 RFCs, Internet-Drafts, or BCP/STD/FYI series in one call.' This cleanly distinguishes it from sibling tools like iana_lookup_pen or iana_search_registries, which target different IANA resources. An agent can tell immediately this is the RFC/draft/series status tool.

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 gives rich input-format guidance (what strings are accepted) and explains the request-limit retry behavior ('failed with reason request_limit, to pass in another call'), which tells the agent when to re-invoke. It does not explicitly name sibling alternatives or state when NOT to use this tool, keeping it out of the 5 range.

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