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

With no annotations provided, the description carries the full burden and does an excellent job. It discloses the return envelope fields, null-handling for unavailable data, symbol format requirements, and pricing, providing comprehensive behavioral context.

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 three sentences, each serving a distinct purpose: stating the tool's function, listing output fields, and noting nulls and cost. It is concise, front-loaded, and has no redundant content.

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?

Even without an output schema, the description thoroughly explains the return envelope and its fields, as well as the behavior for missing fields. It also covers the input symbol variations and cost, making it complete for a single-parameter 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?

The schema provides no description for the ticker parameter, but the tool description fully compensates by explaining exact formatting rules: US symbols are bare (AAPL) and TSX symbols use .TO or TSX:RY form. This is critical information that goes far beyond 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?

The description clearly states 'Get fundamental data for a ticker (profile + key ratios)', specifying the action and resource. This distinguishes it from siblings like get_quote and get_price_history, which focus on different data types.

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 implies usage by stating what data it returns, but does not explicitly mention when to use it over alternatives or provide any exclusionary guidance. It lacks direct comparison to sibling tools, so the usage context is only implicit.

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