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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds meaningful context beyond annotations: the catalog is free, requires no API key, and only the actual replay datasets are paid. No contradiction with annotations.

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 terse sentences deliver the core function first and then add the access/cost caveat. No redundant words or filler.

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 zero-parameter, read-only catalog operation, the description provides all necessary context: what is listed (dates), the domain (SPX market structure), and the free-vs-paid boundary. An output schema is absent, but the simple list nature makes the response type reasonably predictable.

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?

There are zero input parameters, so the schema fully covers invocation. The description's mention of 'no API key required' is access context rather than parameter semantics. Baseline 4 applies because there are no parameters to document.

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?

States a specific purpose: providing a free catalog of available historical SPX market-structure replay dates. It clearly distinguishes the date catalog from the actual replay datasets and the resource/scope is unambiguous. The verb is implied by 'catalog' but the operation is clear.

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 when this tool is appropriate: discovering available dates without an API key, while the underlying datasets are paid. It does not explicitly name a sibling alternative, but no other sibling appears to perform the same date-list function.

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