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

Annotations already establish a safe read-only, idempotent, closed-world operation. The description goes well beyond them by disclosing the five-filter validation pipeline, the exact return shape (`as_leader` and `as_follower`), and the critical behavioral fact that only fully-validated pairs surface and empty lists are common. With no output schema, this is exactly the context an agent needs.

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 front-loaded with purpose, return structure, and the empty-list caveat, and every sentence supports agent decision-making. The enumerated five-filter pipeline is slightly verbose but earns its place by justifying why partial matches are excluded.

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?

Given a read-only lookup with a fully documented single parameter, no output schema, and no annotations gaps, the description is complete: it explains what is returned, how strict validation is, and what an empty result means. Nothing needed to call it correctly is missing.

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 the single `slug` parameter is fully documented in the schema. The description reinforces the lookup intent and the empty-list behavior but adds no syntax or format detail beyond what the schema already provides, making the baseline 3 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?

States a specific verb+resource: fetching statistically-validated leading/lagging relationships for an indicator. The purpose is unambiguous and distinct from sibling lookup tools, but it never explicitly names or contrasts with alternatives like get_indicator or search_indicators.

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?

Usage is implied by the description ('for an indicator', returns split lists) and the warning that most indicators return empty lists usefully sets expectations. However, there is no explicit when-to-use guidance, no when-not conditions, and no named alternative for related lookups.

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