update_recipient

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

With no annotations, the description carries the full behavioral burden. It clearly states that the email is immutable and that existing envelopes retain the original recipient name, which is useful non-obvious behavior. It does not discuss authorization or reversibility, but the key side-effect disclosure is present.

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 tight sentences. The main action is front-loaded, and the second sentence earns its place by disclosing an important behavioral constraint. No redundant wording.

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 3-parameter mutation tool with no annotations and no output schema, the description covers purpose, immutability, and side effects. The only notable omission is explicit routing to create_recipient when the recipient does not yet exist, though 'stored' hints at it.

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 each parameter is already documented. The description adds the high-level 'name or metadata' scope and the email exclusion, but doesn't add per-parameter detail beyond the schema, so a 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 opens with a specific verb and resource: 'Update a stored recipient's name or metadata.' It clearly distinguishes this from creation tools by saying 'stored' and explicitly excludes the email field, leaving no ambiguity about the tool's scope.

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 phrase 'stored recipient' implies the tool is for existing recipients, setting it apart from create_recipient. It also gives a clear exclusion ('The email cannot be changed') and a side-effect boundary ('Existing envelopes are not affected'), giving the agent enough context to decide when to call it. It does not explicitly name an alternative tool, so a small gap remains.

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