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

With annotations already indicating a non-read-only, idempotent, non-destructive operation, the description adds meaningful context: saved keys persist across sessions and are used automatically. It does not contradict the annotations and gives useful side-effect awareness beyond the schema.

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 short sentences with no filler. The core action is stated first, followed immediately by the most important behavioral consequence, making it easy for an agent to parse quickly.

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 moderately simple tool with full schema coverage and helpful annotations, the description covers the essential purpose and persistence behavior. It could be slightly more complete by mentioning that saving an existing name may overwrite it, but the idempotent annotation and schema descriptions reduce the need.

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%, so the input schema already fully documents all five parameters. The description does not need to add parameter detail, and the schema handles meaning for name, label, value, context, and is_default appropriately.

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 uses a specific verb-resource pair, 'Save a credential', and further scopes it to a 'BYOK provider API key' with a clear persistence guarantee. This separates it from the delete/list/default/guide credential siblings even without naming them.

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 implies when to use the tool: when a credential should persist across sessions and be used automatically. However, it does not explicitly contrast with alternatives like credential_delete, credential_default, or credential_list, nor does it state when not to use this tool.

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