list_accounts

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

The annotations already carry the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), and the description goes well beyond them by disclosing the exact return shape (JSON array of E.164 numbers only, no registration status), the fact that it queries the running signal-cli daemon, and the common case of a single account. That is substantive behavioral context an agent needs.

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?

Three short sentences, front-loaded with what it returns, then constraints, then the sibling routing. Nothing redundant; every clause carries 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?

No output schema exists, so the description properly compensates by specifying the return type and its exact contents, plus the daemon dependency and typical cardinality. Nothing an agent needs to invoke it 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?

There are zero parameters and schema coverage is 100%, so the baseline of 4 applies; the description correctly makes no attempt to invent parameters and confirms the call takes no arguments.

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 (List) and resource (Signal accounts registered in signal-cli on this machine), and explicitly distinguishes itself from get_own_number, the closest sibling. An agent can tell exactly which of the 70+ siblings this is without opening a schema.

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?

Names the alternative tool (get_own_number) and the condition that selects it: this tool enumerates all registered accounts, while get_own_number returns the single sending/receiving identity. That is explicit when-to-use/when-not routing.

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