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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, and destructiveHint=false, so the agent knows this is a non-idempotent external write that is not destructive. The description adds one genuinely useful behavioral fact beyond that: the relay design means no direct contact details are exposed. However, it says nothing about the consequences of sending (irreversibility, delivery, visibility to the other party) or about the required conversationToken and how it is obtained, leaving significant behavioral gaps for a message-sending mutation.

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?

It is a single front-loaded sentence with no wasted words, which is structurally sound. The problem is under-specification rather than verbosity: the one sentence cannot carry the tool's purpose, usage, and parameter semantics. It earns its place but is too thin for the job.

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 non-idempotent, externally visible write operation with three undocumented required parameters and no output schema, the description is far too sparse. It does not explain what success looks like, what the conversationToken must be, or what errors to expect. The relay/no-contact-detail note is the only substantive content beyond the annotations.

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 all three parameters are required, yet the description explains none of them. In particular, conversationToken is opaque and its purpose (presumably authorizing the relay) is never clarified, nor is conversationId distinguished from it. The description does not compensate at all for the schema's complete lack of parameter documentation.

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 pairs a specific verb ("Send") with a specific resource ("message") and adds a distinguishing characteristic: it is a relay message sent without exposing direct contact details. That differentiates it reasonably from siblings like report_message or mark_conversation_read. It stops short of explicitly naming which sibling to use instead, so it is clear but not maximally differentiating.

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 when-to-use guidance, no prerequisites, and no mention of alternatives. The agent is not told, for example, when to send a message versus create_inquiry or how this relates to prepare_contact_exchange and confirm_contact_exchange. Only the implicit signal from the verb "Send" indicates usage context.

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