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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: no secret ever crosses the server, the tool takes no arguments, and it returns a specific shape. It also discloses the limitation that credentials cannot be added by the agent, which is beyond the annotations.

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 compact and front-loaded: it states the core purpose first, then the security guarantee, then the return shape, then usage guidance. Every sentence earns its place, and there is no redundant repetition of the title or annotations.

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 zero-parameter read-only tool, the description is complete. It covers what the tool returns, the security behavior, how to use the result, and what to do when the desired credential is absent. The output schema is absent, but the description provides the return shape explicitly, so nothing critical 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?

The tool has zero parameters and schema coverage is 100%, so the schema fully documents the input. The description adds value by explicitly stating 'Takes no arguments' and describing the return shape, which helps the agent understand the tool's contract even though there are no parameters to clarify.

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 states a specific verb ('List') and resource ('source credentials this workspace holds'), and distinguishes itself from the broader sibling set by clarifying it returns credential names, not values. It also explains the relationship to recipes, which makes its purpose unambiguous.

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 explicitly says when to use this tool: to learn which credential names exist for recipes. It also gives clear guidance on what to do if the needed credential is missing (ask the person to paste it at the paste_url) and what not to do (do not ask them to send it directly). This is strong usage guidance.

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