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

Annotations declare readOnlyHint=true and destructiveHint=false, and the description adds valuable behavioral context: it reports status, gives next steps, explains the QR appears in the desktop app, and notes how other tools depend on successful connection. This goes beyond the annotations.

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?

The description is three sentences, slightly longer than minimal, but every clause adds value: purpose, status reporting, QR location, next steps, and dependency on other tools. It is front-loaded with the main purpose and remains readable.

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?

Despite zero parameters, the description fully covers the tool's role: install/sign-in status, instructions, QR specifics, integration with signal_list_chats and signal_read_messages, and the already-connected case. Since an output schema exists, not explaining return values is acceptable.

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 tool has zero parameters, so schema coverage is trivially 100%. The description correctly omits parameter details. Baseline of 4 is appropriate for parameter-free tools.

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 tool's purpose: 'Connect Signal to Local MCP' and reports installation/sign-in status. It distinguishes from siblings like signal_list_chats and signal_read_messages by focusing on setup/connection rather than message operations.

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?

It implicitly provides usage context by noting that 'Once you're signed in, signal_list_chats / signal_read_messages work', which suggests this tool is a prerequisite. It also handles the already-connected case. Does not explicitly name alternatives but the sibling context makes it clear.

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