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

Annotations already establish readOnly/idempotent/non-destructive behavior. The description adds value by disclosing the return structure, the fact that profile_hint is resolved into actual evaluated parameters, the v1 buy-and-hold limitation, and the non-advisory nature of the diagnostic—beyond what annotations provide.

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?

Four sentences, each earning its place: purpose, return contents, v1 scope, resource discovery, and caution about advisory nature. Highly front-loaded, no redundancy, and perfectly sized for the complexity.

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?

Despite having an output schema, the description compensates by detailing the return fields (robustness score, failure-behavior classification, resolved regime parameters). It also covers preconditions (resource for hints), limitations (v1 buy-and-hold), and interpretation (descriptive, not advisory). This is comprehensive for a read-only diagnostic tool.

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 the parameter is already documented. The description enhances meaning by explaining that profile_hint is a 'hint' that gets resolved to concrete regime parameters, which adds the semantic nuance that the schema alone does not convey.

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 opens with a specific verb and resource: 'Run a buy-and-hold backtest against the synthetic stress regime identified by profile_hint.' It clearly distinguishes from siblings by limiting to buy-and-hold and synthetic stress regimes, and it enumerates the return value components.

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 provides clear usage context: it is for buy-and-hold only, gives a prerequisite (discover profile_hint via regimes://available), and notes the diagnostic is descriptive not advisory. It names no explicit alternative tool, but the scope limitation implicitly differentiates it from other stress-test tools.

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