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

Annotations already declare destructiveHint=true, openWorldHint=true, idempotentHint=false, and readOnlyHint=false. The description adds important context beyond them: the simulation emits message.received and STOP, START, and HELP keywords behave as they would for real, which helps an agent understand the side effects.

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?

The description is a single, front-loaded sentence that leads with the critical sandbox-only restriction and then states the action and side effects. Every clause adds relevant information.

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?

For a simulation tool with annotations and no output schema, the description covers the key constraints and side effects. It is slightly incomplete around parameter formats and response behavior, but the essential sandbox and event-emission context is present.

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 only 33%, and the description mainly reinforces the 'to' parameter already documented in the schema. It adds some meaning to 'body' by noting STOP, START, and HELP behave as real keywords, but does not clarify 'from' format or body constraints.

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 uses a specific verb and resource: simulate an inbound SMS. It also states 'Sandbox only' and 'test numbers,' which clearly distinguishes it from production message-sending siblings such as send_message.

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?

It clearly establishes the sandbox-only use case and test-number target, making the intended context explicit. It does not explicitly name a production alternative, but the sandbox constraint effectively excludes non-test usage.

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