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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds context about the return content (positions, PNL, win rate) and optional scoping, which goes beyond the annotations. There's no contradiction, and the read-only behavior is consistent. It would earn a 5 if it mentioned potential edge cases or data ranges, but it's solidly above baseline.

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 a single, front-loaded sentence with zero waste. It immediately states when to use the tool and what it returns, followed by optional scoping. Every word 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 simple, read-only aggregate tool with a rich output schema, two well-documented parameters, and comprehensive annotations, the description is entirely sufficient. It covers purpose, scope, and usage without redundancy, and the output schema handles return-value expectations.

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 100%, and both parameters (period and source) have adequate descriptions. The tool description only says 'optionally scoped by source and period,' which merely restates what the schema already conveys. It adds minimal extra meaning, so the baseline of 3 is appropriate.

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 provides aggregate market stats (positions, PNL, win rate) and mentions optional scoping by source and period. This is specific and uses a clear verb+resource pattern. However, it does not explicitly differentiate from sibling tools like get_signal_stats or get_positions, which could overlap, so it stops short of a 5.

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 phrase 'Use this when the user asks for aggregate market stats' directly tells the agent when to invoke this tool, providing clear context. It doesn't specify exclusions or point to alternative tools, so it lacks the when-not guidance needed for a 5.

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