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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful context beyond those annotations by defining the quadrant methodology, listing the additional metrics returned, and disclosing that free access covers only 11 broad sectors while premium adds 104 thematic/industry sectors.

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 the core purpose, then efficiently defines each quadrant and coverage tiers before pointing to the single-sector alternative. Despite covering several concepts, every sentence supports correct tool selection or interpretation.

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?

With no output schema and no parameters, the description carries the burden of explaining what the tool returns. It describes the quadrant categories, the momentum/relative-strength/return fields, and the difference between free and premium sector coverage, which is sufficient for an agent to use it correctly.

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 there is no parameter semantics to explain. The baseline for a parameterless tool is 4, and nothing in the description introduces confusion about inputs.

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 resource and analysis: each sector ETF's performance versus SPY, organized into four named quadrants. It explicitly distinguishes this scan from zensei_sector_detail, which covers a single sector's holdings.

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?

It clearly indicates the tool is for a cross-sector overview and names the alternative for single-sector holdings: zensei_sector_detail. It also explains the free-versus-premium coverage boundary, which affects whether the agent should expect 11 or 115 sectors.

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