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

Annotations declare idempotentHint=true, but the description adds the crucial qualifier that a retry is only safe with the identical payload and clientMessageId, correcting a naive reading of the annotation. It still omits auth requirements, failure modes, and any note on the open-world (server-forwarding) behavior flagged by openWorldHint.

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 tightly written sentences with zero filler; the destructive action is named first and the retry constraint second. Nothing is wasted or buried.

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 an 8-parameter, all-required, nested-schema mutation tool with 0% parameter documentation, the description is far too thin: it never explains encryptionScheme, encryptionNonce, encryptedKeys, senderDeviceId, or the contextId/chatId distinction. The existing output schema excuses it from describing return values, but the input-side gaps are substantial.

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% across 8 required parameters, including a nested encryptedKeys map, so the description must carry the burden and largely does not. It earns partial credit only by implying clientMessageId functions as the idempotency key, which is real semantic information the schema (a bare string) does not convey.

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 and resource (send a client-encrypted text message), which is clearer than the generic sibling 'send_message' and 'panel_chat'. It does not, however, explicitly distinguish the panel_ variant from the plain send_message sibling, leaving the agent to infer the difference.

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 genuine timing guidance (send only after the user presses Send) and a retry rule, which is useful operational context. It offers no when-to-use / when-not-to-use comparison against the sibling send_message, so usage is only partially covered.

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