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

Annotations already establish this as a safe, idempotent, closed-world read. The description goes beyond them by disclosing catalog size (85 providers), the fact that fees may be quote-only, and the non-obvious filter semantics that excluded providers are silently dropped rather than returned with nulls.

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?

Two sentences, front-loaded with the verb and resource; the returned-field list is dense but earns its place since there is no output schema. Slightly run-on, but no filler.

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?

With no output schema, the description usefully enumerates return fields, and all six parameters are documented in the schema. Minor gaps remain around result ordering defaults and whether unpriced providers surface at all, but nothing an agent needs to call it 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 baseline is 3, but the description generalizes the publish-only rule to both max_monthly_fee_usd and min_countries, while the schema only states it for the fee parameter. That clarification exceeds what the structured data provides.

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?

Names a specific verb (list/filter) and resource (the 85 EOR providers tracked by BestEOR.co) and enumerates the fields returned, so an agent can distinguish it from get_eor_provider or compare_eor_providers without opening the schema.

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?

Implies the browse-and-filter use case and adds an important selection rule ('a fee ceiling or coverage minimum only matches providers that publish that figure'), which warns the agent that filtered results are a subset. It never names when to prefer compare_eor_providers or get_eor_provider instead, so routing is left to inference.

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