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

No annotations are provided, so the description carries the full burden. It usefully discloses a cost of 1 credit and implies a read-style observation lookup, but says nothing about return shape, pagination, default dataset/frequency behavior, error handling, or rate limits beyond the single-credit cost.

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 a single front-loaded sentence with useful examples and a clear cost note. There is no filler or redundant wording.

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 four-parameter data retrieval tool with no annotations and no output schema, the description is too thin. It omits defaults for dataset and frequency, limit behavior, and the relationship to ons_search for finding valid CDIDs.

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 four parameters are at least nominally documented in the schema. The description adds helpful CDID examples, but does not explain the meaning or behavior of dataset, frequency, or limit beyond the terse schema text.

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 and resource: observations for an ONS time series by CDID, with concrete CDID examples such as D7G7 and MGSX. It is clear what the tool retrieves, though it does not explicitly distinguish itself from the sibling ons_search tool.

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 phrase 'by CDID' and the examples imply the tool is for cases where the series identifier is already known. However, it gives no explicit guidance on using ons_search to discover a CDID first, and no when-not-to-use or alternative routing.

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