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

With readOnlyHint=true already declaring a safe read, the description still adds real value: the data returned (counts plus price amount and currency, per month/day), the default time window, and optional channel narrowing. It stops short of covering pagination behavior or auth/rate-limit constraints, so not a 5.

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 compact sentences, front-loaded with the most decision-relevant fact (what data comes back and at what granularity). The default restatement mildly duplicates schema defaults, keeping it just under maximum efficiency.

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?

Nine all-optional parameters at full schema coverage plus a clear statement of the returned metrics and default window means an agent has everything needed to call it; no output schema exists, and the description still summarizes return content adequately.

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% and enums document period_type, channel_type and flow, so the baseline is 3. The description adds the framing 'optionally for one channel' and restates the default monthly/last-3-months behavior that the schema already encodes per-parameter, so it adds little beyond the structured data.

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/resource ('Sent-message counts and money spent per month or per day'), the returned fields (price amount and currency), the granularity, and the underlying endpoint. An agent can distinguish it from the singular smsmode_get_consumption sibling by the plural list semantics.

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 implied through the stated defaults ('monthly, the last 3 months') and optional channel scoping, which tells an agent this is the aggregate-reporting entry point. However, it never says when to use this vs smsmode_get_consumption or when to reach for a different granularity, so no explicit routing guidance is given.

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