SMS balance

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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false), so the bar is lower, but the description adds nothing beyond them. It says nothing about the local-cache behavior implied by the 'fresh' parameter or about latency/staleness of the returned balance figures.

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?

A single compact sentence fragment with no filler, and the most relevant content (limits, used/free, price per part) is front-loaded. It is efficient but verbless, which slightly undercuts its clarity as a standalone definition.

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 usefully enumerates the fields that come back (limits, used, free messages, per-part price), which is the main thing an agent needs. However, for a cached read tool it omits how the 'fresh' flag changes results, leaving a real behavioral gap.

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?

There is a single optional parameter whose schema description ('Skip the local cache') has 100% coverage, so the baseline is 3. The description does not mention caching or freshness at all, adding no meaning beyond the schema.

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 enumerates the data the tool surfaces (limits, used/free messages, price per part) but never states the operation — it is a noun phrase with no verb like 'retrieve' or 'get'. An agent can infer it is a read of SMS balance data, but the purpose is implied rather than declared, and no sibling (e.g. campaign_estimate, campaign_details) is referenced for contrast.

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?

There is no guidance on when to call this tool, no prerequisites, and no mention of alternatives such as campaign_estimate for cost projection. The agent must infer usage purely from the name and the listed data fields.

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