add_device

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals that the operation fails on linked devices, that the new device receives only future messages, and issues a security warning about not sharing the URI. This goes beyond the basic action and fully informs the agent of consequences.

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?

Every sentence serves a purpose: the core action and constraint are front-loaded, followed by the URI source, post-link behavior, verification, and security warning. No fluff—it is thorough without being verbose, appropriate for a tool with security implications.

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 single-parameter tool with no output schema, the description covers all necessary aspects: operation, failure conditions, URI acquisition, post-link behavior, and related tools. An agent has everything needed to decide when and how to call it correctly.

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?

The schema already describes the 'uri' parameter with 100% coverage, so baseline is 3. The description adds valuable context about how to generate the URI (from signal-cli link output or QR scan) and emphasizes its security sensitivity, enhancing the semantic understanding 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?

The description clearly states the action ('Link a new secondary device'), the target ('your Signal account'), and the input mechanism ('using a device-link URI'). It also distinguishes itself from siblings by mentioning list_devices and remove_device as complementary operations, making its purpose unambiguous.

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 specifies when the tool works (only when signal-mcp is the primary device) and when it fails (if set up via signal-cli link), with the exact error message. It provides how to obtain the URI (signal-cli link or QR scan) and directs the agent to use list_devices to verify and remove_device to unlink, covering both context and alternatives.

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