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

Beyond the readOnly/idempotent annotations, the description discloses that only one indicator is computed per call, that symbols can be comma-separated for batch, and that market indices require a paid API key passed via _apiKey. It also states the return type (dated indicator values). These are substantive behavioral details not in the 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 well-structured: it leads with the core purpose, then examples, then the multiple-indicator handling rule, and closes with return type. It is longer than a single sentence but every sentence adds value. Slightly verbose with the example list, but it earns its place for clarity.

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 indicator tool with no output schema, the description covers the essential operational details: single-indicator-per-call, batch support, index key restriction, and return type. It also handles edge cases like multiple requested indicators. Nothing critical is missing for an agent to 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?

Schema coverage is 100%, so each parameter already has a clear description in the schema. The tool description itself adds little beyond examples and the note about index key requirements (which is also in the schema). The baseline of 3 is appropriate because the schema does the heavy lifting and the description doesn't add significant new meaning.

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+resource ('Compute a technical indicator time series') and lists supported indicators. It explicitly names itself as the right tool for any technical-indicator request and differentiates from siblings by scoping to indicators rather than raw price data or quotes. Examples further clarify intent.

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?

It provides explicit when-to-use guidance with concrete natural-language patterns (e.g., 'RSI(14) of AAPL') and states a preference over alternatives. It also instructs how to handle multiple indicators (call once per indicator, don't decline), which is a key usage rule. No exclusions are given, but the guidance is unambiguous.

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