region_start

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

Annotations already declare idempotentHint=true and openWorldHint=false, but the description adds real behavioral context: start time lives in this bridge instance, re-calling with the same name yields already_started:true, and the exact response shape is given. It does not explain why destructiveHint=true is set for what reads as a benign tracker, leaving that annotation unexplained.

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?

Purpose, pairing behavior, idempotency, and return shape are front-loaded in three tight sentences with no filler. The return line earns its place since there is no output schema.

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 single-parameter, no-output-schema tool, the description covers what it does, how it pairs with region_end, the idempotency contract, and the return shape. Nothing needed to invoke or interpret it 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% and the single 'name' param is already documented, so the baseline is 3. The description's note that the same name triggers already_started adds modest semantic weight to the identifier but no format or syntax detail beyond 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 ('Begin tracking an in-process named region') and explicitly names the sibling it pairs with (region_end) for duration calculation, so an agent can distinguish it from other timing/trace tools like start_trace or list_active_regions.

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 relationship to region_end is spelled out ('matched by region_end for duration calculation'), which tells the agent this is the opening half of a paired timing operation. It stops short of explicit 'use this instead of X when Y' routing.

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