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

The description discloses credit spending, background job execution, async return via session ID, and the need for ownership and credit balance confirmation. These go well beyond the annotations (readOnlyHint=false, etc.) and add essential operational behaviors. No contradictions with annotations.

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?

The description is two sentences, front-loaded with the core action and outcome. Every clause carries necessary information (what, return, costs, background job, ownership, precondition) with no redundancy or filler.

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 complex async, credit-spending tool, the description covers the key operational facts: purpose, session ID return, background job, credit cost, and ownership requirement. It does not mention how to retrieve the async result (e.g., via get_simulation_status), but the sibling tool list and output schema partially compensate.

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 the baseline is 3. The description adds a meaningful constraint on ideaId ('pass an ideaId you own') and explains the async/credit context that affects parameter usage, exceeding the schema's bare definitions.

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?

The description uses a specific verb 'Run' with a clear resource ('Time Machine simulation') and outcome ('see how your idea would perform in different eras, returning a session ID'). It distinguishes itself from other run_* siblings like run_arena_duel and run_survival_mode by naming the era-based simulation.

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 description gives clear context for when to use the tool (to simulate ideas across eras) and important preconditions ('pass an ideaId you own', 'confirm your credit balance first'). It also flags 'Not read-only', implicitly distinguishing from the many get_* tools, but does not explicitly name alternative simulation tools as alternatives.

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