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

Annotations already cover read-only, idempotent, closed-world safety, so the description earns credit for adding the auth requirement (Authorization: Bearer) and for enumerating the returned fields, which annotations cannot convey. It omits pagination/ordering behavior, keeping it out of 5 territory.

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?

One front-loaded sentence with no filler; the parenthetical efficiently packs the return fields and the auth note. Slightly dense but nothing is redundant.

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?

With no output schema, describing the returned fields (key, name, aggregation) is the right call, and the auth requirement is a useful operational note. Missing only edge details like whether results are paginated or how many meters are returned.

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 takes no parameters, so the baseline is 4. The description's mention of the aggregation values (sum | count | unique_count) adds meaning about the data model rather than parameter usage, which is a reasonable substitute.

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 and resource ('List the meters on your Usage Lab account') and scopes it to the caller's account, which distinguishes it from get_meter_rollups and create_meter. It stops short of naming siblings explicitly, so a 4 rather than a 5.

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?

Usage is only implied: listing meters is the natural precursor to fetching rollups or creating meters, but the description never says when to pick this over get_meter_rollups. No exclusions or prerequisites beyond auth are given.

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