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

The description complements the readOnlyHint annotation by adding valuable context: 'Updates: monthly' indicates data freshness, and 'history to 1979' clarifies the time range. It also describes the output fields and calculation method. This goes beyond what annotations alone provide, though it doesn't disclose every possible behavioral nuance like exact return types or error conditions, which is acceptable given the read-only nature.

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 extremely concise: two sentences plus a short update cadence note. It packs essential information (what, output fields, data source, when to use, update frequency) without any filler. Every sentence earns its place, and the key action ('Returns') is front-loaded.

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 no output schema, the description provides a complete picture: the purpose, output fields (momentum_score, recent_value, deviation_pct), data source and methodology, historical coverage, update frequency, and explicit use cases. For a read-only data retrieval tool with one optional parameter, this is sufficiently complete for an agent to select and invoke it correctly.

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?

The tool description itself does not explain the 'days' parameter; all parameter semantics are in the schema description, which is comprehensive (100% coverage). Since the schema already documents the parameter fully, the description does not need to add but also does not add anything beyond the schema. This is baseline 3 for high schema coverage.

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 clearly states what the tool does: 'Returns a 0-100 US vehicle-sales momentum score' with specific output fields and calculation basis. It is specific about the resource (US vehicle-sales momentum) and includes data source (FRED TOTALSA). However, it does not explicitly differentiate from sibling tools, so it doesn't fully meet the 'distinguishes from siblings' criterion for a 5.

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 explicit when-to-use guidance: 'Call when the user asks about US auto demand, car or vehicle sales trends, consumer autos, or the auto cycle, or when timing dealer inventory, production planning, or supply-chain stocking decisions around auto-cycle peaks and slowdowns.' This is clear and detailed, but it does not mention when NOT to use it or name alternative tools, so it falls short of a 5.

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