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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds value by disclosing that the tool returns key-construction information (position in the dot-delimited key) and that it is a prerequisite step, which is behavioral context beyond the annotations. It doesn't discuss rate limits or error cases, but for a read-only metadata fetch the annotations plus the description are sufficient.

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?

Three sentences, each earning its place: the first states what the tool returns, the second details the return contents, and the third gives the usage context. The most important information (what it fetches and why it's needed) is front-loaded. No filler or repetition of schema details.

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?

The tool has one parameter, a rich schema description, an output schema, and annotations covering safety and idempotency. The description explains the return value's purpose and the prerequisite relationship to oecd_query_dataset. Nothing an agent needs to decide whether to call this tool and how to use its output 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 the schema already documents flow_ref thoroughly, including the two accepted forms and an example. The description adds context by explaining that the output is needed to construct query keys, which helps the agent understand why flow_ref matters. Since the schema does the heavy lifting, a 4 is appropriate rather than a 5.

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 states a specific verb ('Fetch'), a specific resource ('a dataflow's dimensions'), and the concrete output (dimension names, codelist references, position in the dot-delimited key). It also explicitly distinguishes itself from oecd_query_dataset by saying it is required before calling that tool to understand key structure. This clearly differentiates it from siblings like oecd_get_dimension_values and oecd_query_dataset.

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 explicitly says 'Required before calling oecd_query_dataset to understand key structure,' which gives a clear when-to-use directive and names the alternative it supports. It also implies this is a prerequisite/metadata tool rather than a data-fetching tool, which helps an agent choose it over oecd_query_dataset or oecd_get_dimension_values. No exclusions are needed because the tool's role as a prerequisite is clearly stated.

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