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

Annotations already declare write, open-world, non-idempotent and non-destructive behavior, so the safety profile is covered. The description adds genuinely new traits beyond that: the agent replies, the conversation continues across calls (statefulness), and on_behalf_of is surfaced to the owner.

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; the core action is front-loaded and the persistence note and parameter nudge follow without waste. Every clause earns its place.

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 helpfully states that the agent's reply is returned and that conversation state persists, which an agent needs to interpret results. Annotations cover the rest, leaving little missing for a 3-parameter messaging tool.

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%, so all three parameters are already documented, giving a baseline of 3. The description only reinforces on_behalf_of ('say who you're asking for') rather than adding syntax or format detail 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?

States a specific verb (send) plus resource (message to a fone.me agent) and the outcome (get its reply). The listed intents — question, booking, quote, leave a message — pin down the scope and clearly separate it from find_agents/get_agent, which only discover or fetch agents.

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?

Gives clear usage context through concrete examples (ask a question, request a booking or a quote, leave a message) and notes the conversation persists across calls. It never names find_agents or get_agent as alternatives or states when not to use it, so it stops short of full routing guidance.

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