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

Annotations already mark the tool read-only, and the description adds an explicit anti-fabrication rule: tide times must come only from tool output and must not be estimated from general knowledge. It also discloses the multi-call pattern (one call per place/date range), which is useful behavioral context beyond the schema and annotations.

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 description is long but densely structured with bolded sections for when-to-use, when-not-to-use, required args, typical chain, multi-call, and anti-fabrication. Every section earns its place and the most important scoping 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?

For a tool with no output schema, the description compensates well: it explains the invocation contract, the coordinate vs city modes, exclusions, chaining, and even tells the agent to rely only on returned values. Nothing needed to select and call the tool 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?

The schema already covers 100% of parameters, so the baseline is 3; the description adds value by grouping the either/or requirement (city vs lat+lon), noting which parameters only apply in coordinate mode, and giving station_limit/date range semantics. This goes beyond the schema but the schema was already thorough.

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 description clearly states that this tool answers tide (high/low water) questions for coastal places and explicitly positions it against general world knowledge and sibling tools like get_current_weather. It gives concrete example queries in both German and English, making the resource and scope 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 description provides a dedicated 'When to use' section with positive examples, a 'When NOT to use' section naming get_current_weather and connections/stops, and even warns against inland locations. It also prescribes the typical chain with search_place, leaving no ambiguity about when this tool should be selected.

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