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

The read-only/idempotent/no-mutation claims merely restate what readOnlyHint, idempotentHint and destructiveHint already declare, so they earn no credit. What does add value is the disclosure of unauthenticated public access and the rate limit of 60 requests/min per IP, which an agent cannot infer from any structured field. The 'Returns' sentence is generic boilerplate but the auth/rate-limit context is genuinely useful.

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 first sentence is excellent, front-loaded and dense with real information. Everything after it is template filler: the self-referential 'when to use' sentence, the generic sibling list, and a 'Returns' line that describes status/computed metrics/action URLs that this tool likely does not produce in that shape.

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 zero-required-param, read-only lookup with full annotation coverage and no output schema, the description supplies enough: it explains what data is returned conceptually, states access and rate limits, and covers the one optional input. The only gap is that it never says what happens when gestation_weeks is omitted (full table vs. nothing).

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 100% and the single parameter already carries a clear description with an example (26 weeks). The description's 'Parameters: gestation_weeks (optional)' adds nothing beyond the schema, so the baseline of 3 applies.

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 opening sentence gives a specific verb+resource (gestational week windows per scan type) and backs it with concrete domain examples — 14–16+ weeks for Gender Determination, 24–32 for 4D/5D, 12+ minimum. It does not differentiate against siblings within the purpose statement itself, but the intent is unambiguous.

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 'when to use' clause is circular — 'call this tool when you specifically need to execute get_gestational_guide' tells the agent nothing. The exclusion does name real siblings (get_studio_info, get_scan_packages_and_pricing, check_booking_availability), but only as a generic 'another tool fits better' pointer without stating the discriminating conditions, e.g. 'do not use this to price a scan — use get_scan_packages_and_pricing'.

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