Add an API key

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

Goes well beyond annotations by disclosing that the raw key is encrypted in Supabase Vault, never returned, and that failed probes remain quarantined. These are non-obvious behavioral traits not present in annotations. The description's 'Write; NOT idempotent' aligns perfectly with idempotentHint=false and readOnlyHint=false, with no contradictions.

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?

Three sentences efficiently convey purpose, security, validation, and constraints. Every sentence earns its place, with the primary action front-loaded and no redundant details.

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 mutation tool with 6 parameters and no output schema, the description covers the action, validation, storage, security, and side effects. The main gap is the return value (e.g., whether an ID is returned), but the description gives enough behavioral context to be useful.

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 covers 100% of parameters with descriptions. The description adds modest value by reiterating provider options and the baseUrl allow-list restriction, but doesn't meaningfully elaborate on individual parameter semantics beyond what the schema already provides.

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 the tool's function: 'Add and immediately validate a BYOK API key' for specific providers. This distinguishes it from siblings like remove_byok_key, list_byok_keys, and test_byok_key by emphasizing the add-and-validate action.

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?

Provides clear context: it's for adding new keys, not for testing existing ones. The constraint on baseUrl (only allow-listed OpenAI-compatible HTTPS providers) and the explicit 'Write; NOT idempotent' warning give useful usage guidance, though it doesn't explicitly mention alternative tools.

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