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

Annotations already declare readOnly/openWorld=false/destructive=false, and the description adds substantial context beyond them: sign-in requirement, plan gating, the subscription_required and not_found and rate_limited error paths, a 30/min shared rate limit, and the data source. This is exactly the behavioral detail an agent needs before calling.

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?

Front-loaded with purpose and trigger, then alternatives, then error/auth/rate-limit facts. Dense but every sentence carries operational value; only the trailing 'Not legal advice' and source line are marginally expendable.

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 4-required-param lookup with an output schema, the description covers the trigger, the sibling alternatives, the value encoding of the returned cutoff, and all failure modes (not_found, subscription_required, rate_limited). Nothing an agent needs to call it correctly is missing.

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% and each parameter already carries an enum or exact-value description, so the schema does the heavy lifting. The description's extra detail (the 'C'/'U'/'YYYY-MM-DD' cutoff values) describes the returned field rather than the inputs, so it adds little to parameter semantics beyond the schema. 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?

States a specific verb and resource ('Returns one family- or employment-based cutoff from a month's State Department Visa Bulletin') and names the exact dimensions (chart type, category, country). It explicitly distinguishes itself from get_visa_bulletin_dv and get_visa_bulletin_notes, so an agent can route correctly without opening schemas.

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?

Gives an explicit trigger ('Use it when the user asks whether a priority date is current') and names two alternatives with the conditions that select them (DV lottery cutoffs, advisory notes). Nothing is left to inference.

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