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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the description need not re-state safety. The description adds value by naming the computed metrics (LTV, CAC, ratio) and the optional segmentation, which gives the agent a sense of the output scope. However, it does not disclose behavior like timezone handling (already in schema) or error conditions. The addition of metric names is useful, but not extensive, so a 3 is appropriate.

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 one sentence, front-loaded with the core purpose and then optional segmentation. Every word is necessary; no filler. It is appropriately sized for the tool's complexity.

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?

Given there is an output schema (visible to the agent, though not fully in the prompt) and rich annotations, the description sufficiently covers the tool's purpose and key fields. The only missing element is explicit guidance on when to use it versus other LTV-related siblings, but given the tool's simplicity and the output schema, it is mostly complete for an agent to call 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?

Schema coverage is 100% for all three parameters, with detailed descriptions of each parameter in the schema. The description mentions 'segmented by country' which maps to the segment_by enum but does not add syntax or type details beyond what the schema provides. The description does clarify that only 'country' is available in this release (though the schema is more detailed, it includes other enum values), but the schema description already covers this nuance adequately. Since the schema handles semantics, the description adds minimal value.

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 returns customer lifetime value summary with optional segmentation by country and includes the key metrics (average LTV, CAC, LTV:CAC ratio). It is a specific verb-resource pair ('Get LTV summary') that distinguishes it from sibling analytics tools. The description is concise and action-oriented, leaving no ambiguity about what the tool does.

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 retrieving LTV summaries, but it does not explicitly state when to use this tool versus siblings like get_cac_payback or get_cohort_analysis. There is no mention of prerequisites (e.g., attribution enabled) or when NOT to use it. However, the description does mention the optional segmentation, giving some context. The lack of explicit guidance for alternative tools prevents a higher score.

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