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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real context beyond that: it requires a Proton plan with Bridge installed/signed-in/running, and it clarifies that account credentials are entered via Local MCP's settings window and never pass through the AI — useful operational knowledge.

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?

Front-loaded with the tool's function, then prerequisites and credential-handling context. Every sentence is relevant, though the setup narrative (plan/Bridge install, copying username/password) is more detail than a zero-arg status check strictly needs.

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?

With an output schema present, the description needn't explain return values, and it correctly leaves that out. Combined with the no-param schema and read-only annotations, the definition gives enough to call it and interpret a failure (Bridge not answering), with only the sibling-routing guidance 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?

The tool takes zero parameters, so there is nothing parameter-wise to disambiguate; baseline 4 applies. The description adds no parameter meaning because none exist.

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 (reports) and a precise resource (whether Bridge answers and which Proton accounts are connected to Local MCP). That clearly distinguishes it from siblings like proton_list_emails or proton_send_email, though it doesn't name any sibling explicitly.

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 Bridge-reachability framing implies this is the tool you call to diagnose whether Proton is usable, but it never states when to use it versus alternatives (e.g. proton_disconnect, lmcp_doctor, or the proton_list_emails/read/search tools). Usage is only inferable from the purpose statement.

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