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

With no annotations, the description carries the behavioral disclosure burden. It discloses the tool's nature ('evidence only'), its specific outputs, and limitations (no recommendations, sizing, or venue picks). This adds meaningful context beyond a simple 'returns spread' statement, though it omits potential details like data source or update frequency—acceptable for a read-only, zero-parameter tool.

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 concise and front-loaded, with the core purpose in the first phrase ('Treasury 10Y-2Y spread as evidence only'). It efficiently lists outputs, exclusions, and product positioning in three compact sentences, with no wasted words.

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?

As a zero-input tool with no output schema, the description adequately summarizes the return values (signal_strength, risk_band, reason_codes, allowed/blocked categories) and the evidence-only positioning. It could elaborate on the meaning of 'risk_band' or 'allowed/blocked categories', but for a simple evidence tool, the provided context is largely 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 accepts no parameters, so the description has no parameter semantics to clarify. Per the rubric, a zero-parameter tool receives a baseline of 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?

The description clearly states the tool computes the Treasury 10Y-2Y spread and returns specific evidence outputs (signal_strength, risk_band, reason_codes, action categories). It differentiates itself from advisory tools by explicitly noting 'NO personalised recommendations, NO sizing, NO venue picks' and positioning as 'evidence_infrastructure', though it does not directly name sibling tools.

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 implies usage for evidence-gathering rather than decision-making, explicitly excluding personalized recommendations, sizing, and venue picks. However, it lacks explicit 'when to use' guidance or comparisons to alternatives like yield_curve or yield_curve_v2, so the guidance is implied rather than fully specified.

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