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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds only the data source (NCUA); it says nothing about result volume, whether a CU with no branches returns empty or errors, or geographic coverage — context that would meaningfully reduce invocation uncertainty for an open-world lookup.

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 short sentences with zero filler, and the resource scope is stated first. It is efficient rather than padded, though the brevity leaves gaps that other dimensions penalize.

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 lookup with no output schema, the definition covers what the tool is and its source but never hints at what a branch record contains (address, hours, coordinates) or whether results are paginated. Adequate to trigger a call, thin for planning around the response.

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?

With one parameter at 100% schema coverage, the schema already defines cu_number as an NCUA charter number with an example value, so the description need not repeat it. It adds no meaning beyond the schema — no note on where to find a charter number or how it differs from an FDIC/RSSD identifier, which matters given the sibling bank tools use different ID schemes.

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 names a specific resource — the branch network belonging to a single credit union — and attributes the source (NCUA), which tells the agent this is authoritative U.S. credit-union branch data. However, it omits a verb (list/return) and does nothing to distinguish it from close siblings such as cu_atms or branches, so the agent must infer the resource boundary from the name alone.

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?

There is no guidance on when to choose this tool over cu_atms, credit_union, or the bank_branches_* family, and no stated prerequisites beyond the required charter number. The 'one credit union' scoping is the only implicit routing signal.

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