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

Annotations already declare readOnlyHint=true, so the description adds valuable context: the cost ($0.004 via x402) and the exact access URL, plus the data sources and optional ticker behavior. It does not cover rate limits or output format details, but it goes well beyond the safety annotation.

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 front-loaded with purpose and then packs cost, URL, computation details, and parameter behavior into a single dense sentence. Every element serves a purpose, though the parenthetical URL and price slightly interrupt flow.

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 simple one-parameter tool with no output schema, the description is largely complete: it defines the output (risk-on/mixed/risk-off score), data sources, optional parameter effect, cost, and access method. It could briefly describe the output structure, but the essential information for correct invocation is present.

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 description coverage is 0%, so the description must compensate. It explains that the optional 'symbol' parameter adds the ticker's trend and 21-day relative performance, which clarifies the parameter's effect and implies a ticker symbol value. Format constraints are not specified, but the semantic meaning is clear.

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 verb (provides a market regime score) and resource (risk-on/mixed/risk-off based on SPY/QQQ/IWM/TLT trends and SPY realized volatility). It distinguishes itself from general trend tools by focusing on overall market regime, though it does not explicitly name a sibling alternative.

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?

Usage is implied: the tool is for assessing market regime, optionally with ticker context. However, there is no explicit guidance on when to use this versus siblings like 'trend' or 'setup', nor any exclusions or prerequisites beyond the paid endpoint note.

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