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

Annotations only provide readOnly=false, openWorld=false, idempotent=false, destructive=false, so the description carries the behavioral burden. It adds the fire-and-forget nature ('Send without waiting'), the default of expect_reply=false, and the encryption-switch condition for peers with public keys. This is meaningful context the annotations do not supply.

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?

Four short sentences with the core behavior front-loaded. Each sentence carries distinct value: the async nature, the alternative tool, channel/content prohibitions, and the encryption rule. There is no wasted wording.

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 7-param tool with nested object schemas and no output schema, the description covers the main decision points (when to wait, when to encrypt, channel and content constraints) while the rich schema covers the rest. It omits sparse details like return values or explicit send_file routing, but nothing essential to calling the tool correctly is missing.

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 100%, so the structural baseline is 3. The description's only parameter-relevant points, expect_reply defaults to false and envelope-instead-of-text, duplicate the schema's own descriptions ('default: false', 'Do not also send text'). It adds no real parameter meaning beyond what the already-rich schema provides.

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?

Description opens with 'Send without waiting' – a specific verb and resource (sending a message). It immediately distinguishes itself from the sibling send_and_wait: 'For live chat use send_and_wait.' The envelope-sending mode is also mentioned, making the tool's purpose and scope unmistakable.

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?

Explicitly routes live-chat use to send_and_wait, and gives concrete prohibitions: do not send to a #room, do not send 'ok', and use the e2ee envelope when the peer has an encryption public key. These are direct when/when-not/alternative instructions, far beyond a vague 'use for messaging.'

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