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

Goes well beyond the idempotentHint annotation by spelling out the exact idempotency semantics: exact match after trimming is case-sensitive and includes archived projects, returns created:false, never duplicates, and a retry with the same idempotency_key replays the first answer. It also discloses cost ('Free') and the archived-project constraint.

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?

Dense but front-loaded: purpose, idempotency, archived behavior, cost, and the next-step call are packed into a short block with no filler. The trailing example earns its place for the required name param.

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?

An output schema exists, so return values need not be explained, yet the description still flags the key return signal (created:false). For a create tool with a shared-scope side effect, the description covers permissions-adjacent behavior, idempotency, and the downstream call completely.

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 all three parameters (name, description, idempotency_key) are already documented in the schema, including the trimmed/case-sensitive match rule and the 24-hour idempotency replay. The description's example {"name":"Acme market entry"} adds minor value but does not meaningfully exceed 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+resource ('Open a project') and clarifies the scope model ('they share one vault scope, and each builds on sources earlier ones kept'). It is clearly distinguishable from siblings list_projects and start_run, which it references by name.

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?

Explicit when-to-use guidance: call list_projects first and reuse a fitting project; then pass project.id as project_id to start_run. It also states the when-not case (archived project takes no runs – ask the person to reopen it or pick another name).

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