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

The readOnlyHint=true and destructiveHint=false annotations already establish that this is a safe read operation. The description adds useful scoping ('AgentLot GMV/fees' vs 'external catalog size') but does not disclose additional behavioral details such as whether the stats are computed live, cached, or what the exact response structure looks like. It does not contradict 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?

The description is a single sentence with no filler, and the main object ('AgentLot GMV/fees') appears before the exclusionary qualifier. Every word contributes meaning, and the structure is immediately parseable.

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 zero-parameter, read-only stats endpoint, the description is functionally sufficient: an agent can tell when to call it and roughly what it returns. The lack of an output schema means return-shape details are not provided, but the low complexity and clear scope make this a minor gap rather than a critical omission.

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, so the schema already provides complete parameter information. The description does not need to explain parameter semantics, and the baseline of 4 applies. No parameter-related information is missing.

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 uses a specific verb ('Return') and a concrete resource ('AgentLot GMV/fees'), and it explicitly contrasts this with 'external catalog size', which distinguishes it from sibling tools like search_external_catalog or get_market_stats. Even though the title adds 'real growth stats', the description itself clearly defines what the tool returns.

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 'separately from external catalog size' gives clear context for when this tool is appropriate: when the agent needs AgentLot-specific GMV/fees rather than external catalog metrics. It does not explicitly name alternatives or state 'use X instead', but the contrast is enough to guide selection among the many sibling tools.

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