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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely non-derivable behavior: businesses with dead domains/404s are excluded entirely, results are timezone-local to the destination, and only venues with verified hours appear so a short list signals thin coverage rather than an empty city. That last point directly prevents a downstream hallucination.

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 the core definition and the sibling routing up front, and every sentence carries information. It loses a point for redundancy: 'a short list means thin hours coverage, NOT an empty city' and 'Never tell a traveller nothing is open' make the same point twice, and the all-caps emphasis is doing work that tighter wording could.

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 and no annotations covering data shape, the description compensates well on the caveats that matter most (coverage thinness, exclusion of defunct businesses). It does not describe result ordering or whether distance from 'near' is reflected, which an agent might want when picking a limit, but nothing critical to correct invocation 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 description coverage is 100%, so all five parameters (near, limit, category, destination, bookable_only) are already documented in the schema. The description adds only indirect meaning — that 'destination' drives the timezone used for the open-now computation — and says nothing about limit, category, or bookable_only semantics. Baseline 3 applies when the schema does the heavy lifting.

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+resource+scope: places that are open right now in a destination, with the computation basis (destination's own timezone). It also explicitly names the sibling it is not — 'Use search_places for the full directory' — so an agent can distinguish it from search_places without opening either schema.

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?

Explicit routing: use this for what's confirmed open now, use search_places for the full directory. It also gives a hard usage constraint — never tell a traveller 'nothing is open' based on this tool — which is a when-not-to-use rule an agent could not infer from the schema.

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