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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds ordering (oldest first), timezone handling (local times), a summary, and constraints on days (max 365) and end_date format (YYYY-MM-DD). These are valuable 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?

Two sentences with no filler. The primary purpose is stated first, followed by the time-window constraint. Every word adds value.

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?

Output schema is present, so return format is covered externally. The description covers the input constraints (days range, date format, default) and key behavioral traits (order, local times, summary). It does not mention pagination or error handling, but these are unlikely to be needed given the output schema and scope. Overall, complete for typical usage.

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%, so the description must compensate. It explains days (max 365) and end_date (format and default), but does not describe the 'key' parameter beyond implying it identifies the metric. The required parameter lacks explicit semantics, leaving some ambiguity.

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?

States a specific verb ('Get') and resource ('one custom metric's entries'), with behavioral details (oldest first, local times) and a summary. The contrast with list_custom_metrics is clear: this returns entries for a single metric, not a list of metrics.

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 makes it clear that this retrieves entries for one metric, but does not explicitly contrast with sibling tools like list_custom_metrics or mention when to prefer this tool. No exclusions or alternatives are named, so guidance is implied rather than explicit.

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