What Reservoir covers

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

Annotations already establish readOnly, idempotent, open-world behavior, so the safety bar is low. The description adds meaningful non-obvious content: it discloses the specific fields returned (venue first/newest day, update schedule, AWS cost) and the fallback behavior of pointing to an alternate API endpoint when a topic is absent.

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?

Two compact sentences with no filler, and the coverage scope is front-loaded before the topic-routing behavior. The noun-pile style is dense but readable and every clause conveys content.

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 defining return values and annotations covering safety and idempotency, the description only needed to convey scope and topic routing, which it does. It could be slightly stronger by noting the no-argument default (full catalog), but nothing essential 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%, including the venue enum list and a full explanation of `topic`, so the schema carries the parameter burden. The description restates the topic behavior without adding syntax, defaults, or format detail beyond the schema, making baseline 3 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?

The description names the specific resource it reports on (datasets, bucket paths, market naming, venue date ranges, update schedule, AWS cost), which clearly distinguishes it from sibling data-retrieval tools like reservoir_query or reservoir_candles. It is a telegraphic noun list rather than an explicit verb+object, but the intent (report Reservoir's coverage/catalog) 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?

It explains the conditional behavior of the `topic` argument ('says whether Reservoir holds it and, if not, which Hydromancer API endpoint does'), which is a form of routing guidance. However, it never states when an agent should call this tool versus the sibling data tools (e.g., before querying, to discover venues), and gives no exclusions.

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