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

The description goes well beyond the readOnlyHint annotation by disclosing concrete behavioral constraints: 500-row and 20-second limits, history restricted to 2025-01-01 onward, certain tick-level tables excluded, and the fact that results indicate which limit was reached. It also explains the API-key-dependent behavior shift, providing substantial transparency.

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 compact and information-dense: three sentences cover the core action, authentication behavior, limits, exclusions, and result reporting. Every sentence earns its place, and the primary function is front-loaded clearly.

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 single-parameter tool, the description covers the database target, read-only scope, authentication options, hard limits, exclusions, and what the caller receives. It does not detail the exact row/error response format, but 'get the rows back' plus the limit-disclosure note is sufficient for most invocation decisions.

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 for the single sql parameter is 100%, with the schema already describing it as 'A single SELECT statement.' The description confirms the read-only ClickHouse SELECT nature but adds little semantic detail about the sql value itself beyond what the schema provides, so the baseline score of 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 opens with a specific verb and resource: 'Run one read-only ClickHouse SELECT against the global_markets database and get the rows back.' This makes the tool's function unmistakable and differentiates it from the sibling schema/plan tools by focusing on executing SELECT queries rather than inspecting metadata or plans.

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 operating context: no key is needed for the default limits, connecting with an API key changes behavior, and the access limits are spelled out. It does not explicitly name alternatives or say when not to use this tool, but the SELECT-versus-describe/list/get distinction is strong enough to guide an agent.

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