update_device

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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=true) by disclosing the side effect (visible in every device's Linked Devices list), the primary-device precondition for renaming other devices, that messaging is unaffected, and the returned fields (status, device_id, name).

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 purpose, then precondition, then scope note and alternatives in a tight sequence with no filler. It is dense and slightly long, but nearly every clause carries actionable information (the quoted error string is the only borderline item).

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 two-parameter mutation with no output schema, the description covers purpose, precondition, failure mode, side effects, and return fields, and routes to alternatives. Nothing an agent needs in order to call 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?

Schema description coverage is 100%, so both parameters are already documented. The description restates device_id as coming from list_devices and name as the new label, adding only marginal context beyond the schema, so the baseline 3 applies.

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+resource ('Rename a device on your Signal account') and immediately scopes what the name affects (the Linked Devices list on every device). It is clearly distinguishable from siblings like update_profile or remove_device, which it names 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?

Gives explicit routing: use remove_device to unlink, use update_profile to change profile name. It also states the precise precondition under which the tool works versus fails, including the exact error text 'This command doesn't work on linked devices'.

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