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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds useful context about returned fields (endpoint, auth method, health probe), but does not disclose additional behavioral aspects such as error handling or access restrictions, which is acceptable but not exceptional.

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 a single front-loaded sentence that names the action, resource, selection key, and key return contents without redundancy. Every phrase earns its place, and there is no filler or repetition of the title.

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 simple read-only operation with one parameter and read/idempotent annotations, the description is sufficient: it explains what is fetched, how it is selected, and what key fields are included. It omits details about not-found or error behavior, but that is a minor gap given the tool's simplicity.

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 the slug parameter already has a clear description with an example. The description's phrase 'by slug' reinforces the parameter's role but does not add new semantic detail beyond what the schema provides, matching the baseline for high schema coverage.

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 ('Fetch') and a specific resource ('one approved Agent Nexus registry entry by slug'), which distinguishes it from sibling tools like search_registry and list_categories. The phrase 'by slug' pinpoints the unique access pattern and makes the tool's role immediately clear.

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 clearly implies this tool is for retrieving a single known entry when the slug is available, rather than for discovery or broad searching. It does not explicitly name alternative tools or provide when-not-to-use guidance, but the slug-based 'one entry' framing provides clear context and no misleading cues.

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