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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: provenance ('from its own site'), editorial neutrality ('Listed, never ranked; no one pays to be here'), which tells the agent results are unfiltered and unbiased. It stops short of stating result count defaults or pagination behavior.

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 purpose is front-loaded in the opening clause, which is good, but the long enumerated list of place types largely duplicates the category enum already in the schema, and the marketing-tinged framing ('no one pays to be here') takes space without helping selection. It is one run-on sentence plus fragments rather than a structured statement of capability.

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 an output schema present, the description needn't detail return values, yet it usefully notes each entry carries description, address, phone and website. Annotations cover safety, so the remaining gaps are minor: default limit, result ordering, and whether multiple filters intersect are unstated.

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 50% — query and category carry descriptions, while island and limit have none. The description's 'search by words, island or category' maps the filters to intent but adds no semantics about how filters combine (AND vs OR), what happens when island='all', or the default value of limit. Baseline 3 for this coverage level 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 — 'The island directory' with a search interface over 228 real places across five named islands — and enumerates the entity types covered. An agent can tell this is a business/place lookup tool and distinguish it from siblings like happenings or island_market without opening the 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?

The final sentence, 'Search by words, island or category,' describes how to invoke the tool but not when to prefer it over overlapping siblings such as island_market, happenings, or get_neighborhood. No when-not conditions or prerequisites (e.g., that all parameters are optional and it can be called with no filters) are stated.

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