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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: the credit cost tiers (5/8/13 credits by depth) and the 'No data = no charge' policy. It also clarifies the output is monthly time-series data. This goes beyond the annotations and helps the agent understand cost implications.

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?

Three sentences with zero waste. The core purpose is front-loaded, the credit tiers are compactly stated, and the 'No data = no charge' policy is a single short sentence. Every sentence earns its place.

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 read-only, idempotent tool with a fully documented schema, the description is nearly complete. It covers the data type, the depth tiers, and the cost policy. The only minor gap is that it doesn't describe the exact return shape (e.g., array of monthly objects), but since there is no output schema and the tool is simple, this is a small omission.

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 schema already documents all three parameters (domain, months, signal) with descriptions and constraints. The description adds the credit-tier meaning of the 'months' parameter and the two signal enum values, but it doesn't add syntax or format details beyond what the schema provides. Baseline 3 is appropriate.

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 states a specific verb ('get'), a resource ('monthly time-series of price changes or stock-status flips'), and a scope ('for a brand'). It also distinguishes the two signal types and the depth tiers, so an agent can tell it apart from siblings like get_brand_snapshot or get_competitor_price without opening the schema.

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 clearly implies when to use this tool: when a brand's historical price or stock-status signal is needed. It does not explicitly name alternatives or exclusions, but the sibling list and the specific signal types provide enough context. A clear 'use this for time-series history' statement is present, though it lacks explicit when-not-to-use guidance.

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