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

Annotations declare non-readonly and non-idempotent; the description earns extra credit by explaining the concrete consequence — multiple stopwatches can run simultaneously, so calling it again creates another timer rather than replacing one. It adds no permission, side-effect, or error info beyond that.

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?

Two short sentences, front-loaded with the parallel-run behavior, then the optional ticket hint. Every clause carries information an agent would otherwise have to infer.

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 simple two-optional-param creation tool with no output schema, the description covers the parallel-running semantics and the deferred ticket workflow, which are the non-obvious behaviors. Nothing an agent needs 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 coverage is 100%, so both params are documented, but the description adds real meaning: ticket_id is genuinely optional and can be attached later at booking, which the schema only hints at with '(optional)'. The title default behavior is left to the schema.

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 ('Starts a new stopwatch for the user') and adds a distinguishing scope note: it runs in parallel with existing stopwatches rather than replacing them. It doesn't explicitly name siblings like resume_stopwatch or book_stopwatch, so it stops short of full differentiation.

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 clear context for when to use it (starting a fresh stopwatch alongside others) and clarifies that the ticket link is optional and deferrable to booking. It doesn't name an alternative tool or state a when-not condition, so the exclusion guidance is absent.

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