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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds 'raw' and 'for a date', but does not disclose additional behavioral details like pagination, rate limits, or return format. It provides modest value beyond 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 concise sentence with no wasted words. It is front-loaded and clear, though it lacks a verb and is somewhat under-specified for full clarity.

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 the tool's simplicity, an output schema, and strong annotations, the description is minimally adequate. However, it omits usage context and parameter semantics, leaving clear gaps for an agent trying to decide when to invoke it.

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%, and the description only hints at the date parameter without explaining its format or the user_id parameter. The tool has 2 required parameters, and the description fails to compensate for the lack of parameter documentation in the schema.

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 'Raw heartbeats for a date' clearly indicates the tool retrieves raw heartbeat data filtered by date. The resource is specific, but it lacks an explicit verb and does not differentiate from sibling tools like durations or summaries beyond the term 'raw'.

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 provides no guidance on when to use this tool versus alternatives such as durations or summaries. There is no mention of prerequisites, typical use cases, or exclusions, leaving the agent to infer usage from the schema.

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