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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, covering safety and idempotency. The description adds valuable behavioral context beyond annotations by disclosing that sensitive fields are masked and that the LLM never sees the secret directly, which is critical for the agent's decision-making. No contradiction exists.

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 two sentences long, with the core purpose in the first sentence and critical behavioral guidance in the second. It is front-loaded and contains no filler. Every sentence earns its place, making it efficient and easy to parse.

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?

The tool is a simple get-by-ID operation. With an output schema present, the return format is documented. Annotations cover safety and idempotency. The description adds the crucial masking behavior and the alternative for plaintext, which fully equips an agent to decide when to call this tool and what to expect. Nothing essential is missing for correct invocation.

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 input schema provides full 100% coverage with descriptions for both 'id' and 'agentId'. The description does not add additional meaning beyond the schema—it merely restates that the tool fetches by ID. Given the high schema coverage, the baseline of 3 is appropriate, and the description does not compensate for any gaps because none exist.

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 clearly states a specific verb ('Get'), a specific resource ('vault credential'), and the retrieval method ('by ID'). It differentiates from siblings like vault_credential_list and vault_credential_search by focusing on a single credential lookup. The purpose is immediately 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 provides explicit context on when to use this tool versus needing plaintext access: it states that sensitive fields are masked and instructs to mint a vault token at the credential broker for plaintext needs. While it doesn't name a specific sibling tool, it clearly distinguishes the use case and directs the agent to an alternative workflow when plaintext is required.

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