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

Annotations already provide read-only, open-world, idempotent, and non-destructive hints. The description adds a useful behavioral detail—that the returned slugs are intended for use with get_series—but it does not describe response format, ordering, pagination, or coverage guarantees beyond the 'every' claim.

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?

One compact sentence conveys purpose, scope, examples, and the relationship to get_series. Every phrase earns its place; no redundant filler or restatement of the title.

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 no-parameter, no-output-schema list tool, the description gives enough to understand what will be returned and how to use it. An explicit note about pagination or response limits would be a minor enhancement, but the presence of the open-world and idempotent hints reduces the need.

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 tool has zero parameters, so the schema already covers everything parameter-related. The description correctly omits parameter details because none exist; the baseline for 0-param tools is 4.

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?

Description states a specific verb ('list') and resource ('every US economic data series Helios tracks'), with concrete examples. It clearly distinguishes from siblings by explaining it returns the catalog of series plus the slug, not the series data itself.

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 explicitly links the output to get_series (the slug is for get_series), which tells the agent this tool is for discovering available series before retrieving a specific one. It does not mention explicit exclusions or when not to use, but the workflow direction is clear and sufficient given the sibling set.

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