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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=false, so the safety/behavior profile is fully covered by structured data. The description usefully adds that this is a discovery-style prerequisite to `series` and enumerates the returned attributes, though it says nothing about result size or ordering.

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 short sentences, zero filler, and the payload description is front-loaded ahead of the routing instruction. Every clause carries information.

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?

There is no output schema, so the description must carry the return-value burden, and it does name the three returned attributes including the kind and unit enumerations. It stops short of describing the response shape or ordering, a minor gap for a static zero-parameter list.

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 takes zero parameters, so the 4 baseline applies. The description mentions no inputs, which is correct here; its field list (label, kind, unit) describes outputs rather than parameters, so it neither adds nor detracts from parameter semantics.

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?

Specific verb-plus-resource: it enumerates every standard series slug accepted by the sibling `series` tool, and names the payload fields (label, kind level/spread, unit %/bps). An agent can distinguish it from `series`, `rate_details`, and `rate_history` without opening any schema.

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?

States the exact condition for calling it ('when you do not know the slug') and names the alternative (`series`) as the follow-up. The inverse case (slug already known → skip straight to `series`) is directly implied by the conditional phrasing.

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