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

With no annotations, the description carries the full burden, and it does disclose the most important trait: the key persists for the remainder of the connection rather than applying to one call. It does not say what happens on an invalid or malformed key, whether a previously set key is overwritten, or whether the key is bound to the session. Those gaps matter for a state-mutating credential tool.

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?

Two short sentences, front-loaded with the condition and the effect, with zero filler. The exclusion about sign_up is placed where an agent will read it before deciding to call.

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 one-parameter, no-output tool this covers the decision and the durable effect of the call. It falls short only on failure behavior and overwrite semantics, which an agent would want before re-using this on a connection that may already have a key.

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 coverage is 100% and the schema already documents the single parameter, including the 'nod_sk_' prefix. The description adds only provenance (the key came from sign_up or create_key), which is mildly useful but not beyond what the structured fields imply. Baseline 3 is appropriate.

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 action and effect: pass an existing NodNod API key here once and 'the rest of this connection uses it.' It also names the sibling tools that produce such keys (sign_up, create_key), so an agent can place it relative to them. It is slightly less crisp about whether it attaches, validates, or replaces a key, which keeps it below a 5.

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?

It gives a clear positive condition ('if you already have a NodNod API key from an earlier sign_up or create_key') and an explicit exclusion ('not needed right after sign_up'). What it leaves implicit is the inverse route: if the agent has no key, it should go to sign_up or create_key instead of calling this.

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