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

Annotations already declare the tool read-only, idempotent, and non-destructive. The description adds useful behavioral context beyond those annotations: the catalog is versioned, and the 'probable' index is a legacy comparison weight rather than an empirical probability. This materially prevents misuse without contradicting the 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 sentences with no wasted words. The core return object is front-loaded in the first sentence, and the disambiguating caveat about the editorial index is placed second. Every sentence earns its place.

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 read-only, zero-parameter, low-complexity tool, the description is complete: it says what is returned, how to interpret the potentially misleading 'probable' label, and how the result relates to score_headline. No output schema exists, but the simplicity of the tool makes this sufficient.

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 and an empty input schema, so parameter semantics are fully covered by the schema. Per the baseline for zero-parameter tools, a score of 4 applies; the description's substantive content is about return semantics, not parameters.

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 action ('Return') and a specific resource ('versioned category and event-class catalog'), and explicitly ties it to score_headline. It also clarifies that the 'probable' in the title is not an empirical probability, removing a likely misinterpretation.

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 gives clear context by identifying the catalog as the one used by score_headline, which tells an agent when this tool is relevant. It also warns against treating the editorial index as a probability. It does not explicitly name alternative tools or say when not to use it, but the sibling context makes the boundary reasonably clear.

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