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

Beyond the annotations, the description discloses that the credential is checked once and dropped, that only an account id and a minted client key are stored, that unlink_account revokes the binding, and that possession of the client id becomes a credential. This is exactly the behavioral context an agent needs for a linking operation.

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 longer than average but front-loaded and well-structured with bold lead-ins that make it scannable. Nearly every sentence carries setup, security, or eligibility guidance; only the stray trailing 'Free.' feels extraneous.

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 mutating, auth-related tool with no output schema, the description covers prerequisites, eligibility, both proof methods, credential lifecycle, revocation, and security warnings. An agent has everything needed to decide whether and how to invoke it correctly.

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 schema already covers both parameters with examples, constraints, and lifecycle details, so the baseline is 3. The description adds selection guidance—api_key when the key is on hand, link_code when the user prefers not to paste a key—and connects link_code to create_account, which raises it above baseline.

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 opens with a precise statement of what the tool does: 'Point this MCP client at an account you already have' and ties it to a concrete effect (stopping header-less calls from spending the keyless trial). The title and body also clearly separate it from create_account and unlink_account.

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 explicitly says when to use this tool (clients that cannot set HTTP headers), tells the agent to prefer a header-based approach when possible, and states the eligibility requirement that the client have an identity of its own. It also gives two concrete ways to authenticate and when to choose each.

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