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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the description doesn't need to repeat safety. It adds useful behavioral details: limits (up to 5 series, up to 10 years with registered key), return format (year, period, period name, numeric value), and licensing/cost (public domain, no upstream cost). These go beyond annotations and help the agent understand constraints and output shape.

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 dense but efficient. It opens with the core purpose, then lists limits, return format, examples, and a resource link, all in a logical order. Every sentence adds information without redundancy. It could be slightly trimmed (the licensing note might be considered extra), but it remains well-structured and 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?

Given the tool's moderate complexity (3 params, no enums, has output schema), the description covers the essential context: what it does, limits, return shape, and examples. It doesn't address error handling or edge cases (e.g., invalid series IDs), but that's not required. The presence of an output schema likely covers return details, so the description is sufficiently complete for an agent to select and call it correctly.

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 coverage is 100%, so the baseline is 3. The description adds value by providing concrete examples of valid series IDs (CUUR0000SA0, etc.) and clarifying the year-range constraint (up to 10 years with a registered key) that is only partially in the schema. This enriches the agent's understanding of what the parameters expect, though the schema already describes each parameter adequately.

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 the tool fetches BLS time series by series ID, names the specific resource, and provides concrete examples of common series IDs. It distinguishes itself from specialized siblings (e.g., bls.macro.cpi) by being the generic series lookup, though it doesn't explicitly reference them. The verb 'fetch' and resource 'time series' are specific and 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 explains the mechanics (up to 5 series IDs, optional year range, up to 10 years with a key) but does not explicitly state when to use this tool versus the specialized BLS siblings (bls.macro.cpi, bls.macro.payrolls, bls.macro.unemployment). There is no mention of alternatives or exclusions, so an agent might not know that specialized tools exist for common series. The context implies general use, but explicit guidance is missing.

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