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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the description needn't restate safety. It does add real value beyond them: it discloses that values are 'recomputed from raw events' (freshness/provenance), states authentication is required, and enumerates the returned quantities and event_count.

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 compact sentences, front-loaded with the core purpose, followed by return shape and the auth prerequisite. Nothing is redundant with the schema and no sentence is filler.

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, the description correctly compensates by naming the returned fields, and it notes recompute provenance and the API-key requirement. Minor gaps remain around result-set size or limits and error behavior when a meter key is invalid, but for a low-complexity aggregate read this is nearly 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 coverage is 100%, with each parameter already documented including the YYYY-MM pattern and current-month default, so the schema does the heavy lifting. The description adds only marginal meaning by framing 'subscription' as a customer filter and emphasizing single-meter scope, which is the expected baseline when the schema is complete.

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 ('Monthly totals per customer for one meter'), scopes it to a single meter, and names the underlying endpoint GET /api/v1/meters/{meter}/rollups. An agent can immediately tell this is an aggregation read, distinct from sibling tools like record_usage_events or list_meters.

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: the scope phrase 'for one meter' and the optional subscription filter suggest when this tool fits, but there is no explicit when-to-use or when-not-to-use guidance, and no named alternative for multi-meter or raw-event needs. 'Needs your API key' adds a prerequisite but not routing guidance.

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