Start a profile

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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that: the browser is launched under the profile's own proxy and fingerprint (so session identity matters) and it 'Asks the user first', a confirmation behavior the annotations do not express. It omits what happens if the profile is already running, which matters given idempotentHint=false.

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, zero filler, with the core action and its defining traits front-loaded before the lifecycle note. Nothing could be removed without losing 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?

For a start/stop lifecycle tool with no output schema, the description covers action, prerequisites and teardown. The one gap is that it does not say what a successful start yields (e.g. whether the running session is then driven via the page_* tools), which would help an agent chain calls, but nothing required for correct invocation 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 coverage is 67% and the schema already documents url ('Page to open first') and headless ('Run without a window'); the description largely restates these as 'optionally at a URL and optionally hidden (headless)'. The required id is undocumented in both places but is self-evident from the resource name. Baseline 3 is appropriate.

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 and resource ('Opens a profile's browser') plus the two defining attributes (own proxy, own fingerprint), which is exactly what differentiates it from create_profile or get_profile. It also names the terminating sibling, stop_profile, so the agent can place it in the lifecycle 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?

Gives a clear when ('when you are done' -> stop_profile) and a precondition ('Asks the user first'), which is actionable context. It stops short of an explicit exclusion, e.g. when to prefer start_warmer or when a profile is already running, so it does not reach the full when/when-not/alternatives bar.

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