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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds genuinely non-obvious behavior: newest-first ordering, an ambiguity fallback that returns a list to choose from, and the guarantee that registrations are never merged. It does not say what happens when neither selector is supplied.

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?

Three tight sentences: return shape first, then how to query, then the ambiguity edge case. No filler and the most decision-relevant information is front-loaded.

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 correctly enumerates the returned fields (date, type, foreign principal, document link) and the ordering. The gap is that all three parameters are optional, yet the description never says what happens if neither registration nor firm is passed.

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 baseline is 3, but the description adds real meaning: registration is 'the registration number other tools return' (chaining guidance) and firm is 'matched exactly', a matching-semantics detail the schema only hints at with an example. limit is left entirely to the schema.

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?

Specific verb+resource+scope: 'every document a FARA registrant has filed with the Justice Department, newest first', plus the exact fields returned. It also implicitly separates itself from the sibling foreign_agents by operating on one registrant's filing history rather than on agents themselves.

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?

Explicitly states the two invocation modes ('pass registration ... or firm') and the disambiguation behavior when a firm name maps to several registrations. It lacks an explicit 'use this instead of foreign_agents when...' routing sentence, which keeps it short of a 5.

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