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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the safety profile is fully covered. The description adds one useful fact beyond the annotations: only "published" listings are retrievable. It says nothing about behavior for an unknown or unpublished slug (error vs. empty).

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?

A single eight-word sentence with the operation, scope, and key front-loaded. No filler, nothing redundant.

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 one-parameter read tool with full annotation coverage this is nearly adequate, but with no output schema the description could reasonably indicate what a listing contains or what happens when the slug matches nothing. Those gaps are minor but real.

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 description coverage is 100% and there is a single parameter, so the schema already defines the slug format, pattern, and length. The description only confirms slug as the lookup key, adding no syntax or format detail 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?

States a specific verb ("Get"), resource ("one published credit union"), and lookup key ("by its slug"), which cleanly separates it from list_*/search_listings siblings. It stops short of explicitly naming the alternative (search_listings) for multi-result lookups, so it falls just shy of a 5.

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 singular "one ... by its slug" implies this is the exact-identifier lookup rather than a search, but no when-to-use or when-not-to-use guidance is stated and no alternative is named. Usage is inferable but not spelled out.

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