Send an eXpress message

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

Annotations already indicate a non-read-only, external, destructive, idempotent operation. The description adds meaningful context beyond those hints: the message is encrypted, the write is external, it is gated by an environment variable, and it requires MCP host approval. No contradiction with annotations is present.

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 tight sentences: the first states the core action and identity, the second gives the critical operational caveat. There is no filler or repetition of schema 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?

Annotations cover safety and idempotency, and the description covers the unusual external-write gating and approval requirement. However, with no output schema and no parameter-level guidance in the description, the agent still lacks information about return behavior and the meaning of scope/idempotencyKey.

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%, so the description must carry parameter meaning. It only hints at the 'text' parameter by saying 'text message' and says nothing about chatId, scope, or idempotencyKey. The required idempotencyKey and the scope enum are left entirely to 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?

The description clearly states the verb and resource: 'Encrypt and send a text message as the authenticated eXpress user.' It unambiguously differentiates this from the sibling tools by saying this is a send operation, not listing, status, or history retrieval.

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?

The description implies usage when the agent needs to send an eXpress message and gives important preconditions: the feature is disabled unless EXPRESS_ENABLE_SEND=1 and requires MCP host approval. However, it does not explicitly contrast this tool with siblings or state when not to use it.

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