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

Annotations already establish readOnly, idempotent, non-destructive, and non-open-world behavior. The description adds genuinely new context beyond that: it guarantees phone numbers and private consent records are never returned, and clarifies it does not send or reserve quota. This is useful privacy and side-effect disclosure, though it doesn't cover pagination or result size.

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 tight sentences, each earning its place: scope of what is read, privacy exclusion, and usage/side-effect clarification. The core purpose is front-loaded with zero 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 carries the burden of describing returns, and it does so by enumerating guests, hosts, exclusions, sender identity, and remaining allowance. Combined with the privacy and no-side-effect notes, an agent has enough to call it correctly, though return format specifics remain absent.

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 0% and there is one required parameter (event_id). The description's phrase 'for a managed event' loosely ties the parameter to a managed event, but it adds no format or scoping detail beyond the schema's pattern. Baseline 3 given the near-total reliance on 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?

States a precise verb (Read) and enumerates the exact resource contents (eligible SMS guests and hosts, exclusions, sender identity, remaining allowance for a managed event). An agent can easily distinguish this read-only audience tool from send_sms_announcement and preview_sms_announcement among the siblings.

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?

Provides clear context: 'Read before composing an SMS' and explicitly disclaims sending or reserving quota, which routes the agent away from the send/preview siblings. It stops short of explicitly naming an alternative tool, but the when-to-use condition is unambiguous.

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