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

Annotations declare readOnly, idempotent, non-destructive, closedWorld. The description adds valuable behavioral context beyond annotations: gaps are real gaps, never filled; unknown key returns similar keys and full archived list. This is useful operational detail.

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?

Three sentences, front-loaded with purpose, then key behavioral traits. No wasted words, though could be slightly tighter.

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 read-only metric history tool with no output schema, the description covers granularity, gap behavior, and error fallback. Missing: explanation of the 'range' parameter's effect, and return format details (though no output schema so some burden is on the description). Overall fairly complete.

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 50%. The 'key' parameter is described in the schema itself with examples. The 'range' parameter has no description in the schema and is not mentioned in the description. Baseline 3 is appropriate since the schema partially documents parameters and the description adds some context about the archive.

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 identifies a specific resource ('history of one measured metric from the ledger's archive') and indicates the granularity (daily points, 5-minute points for last 48h). It distinguishes itself from vague siblings, though without explicit sibling differentiation.

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?

Implied usage: when you need historical metric data. But no explicit when-to-use vs alternatives, prerequisites, or exclusions. A reader knows what it does but not necessarily when to choose it over other tools.

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