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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses that the signature belongs to the address, is shared by everyone writing from that address, and applies to messages being composed rather than retroactively, but it omits permissions, authorization requirements, and exact effects on existing messages.

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?

At two sentences it is appropriately sized and front-loads the core action, but the metaphorical phrasing ('the block that closes what is written from an address', 'added behind the sender back') makes it less immediately clear than a direct description would be.

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 simple two-parameter mutation with no output schema and no annotations, the description covers the shared-address behavior and non-retroactive application. It still leaves gaps around authorization and any side effects on already-composed messages, so it is adequate but not complete.

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 both parameters (address and signature) are already documented in the schema, including that an empty signature removes it. The description adds no additional parameter semantics beyond what the schema provides, making the baseline 3 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 conveys that this writes a closing block associated with an address, i.e., a signature, but it uses metaphorical language ('writes the block that closes what is written') rather than naming the resource directly. It does not differentiate this tool from any sibling tool.

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 one usage nuance: the signature is applied when a message is being written and is not retroactively inserted behind the sender's back. However, it gives no explicit guidance on when to choose this tool versus alternatives or what prerequisites exist beyond the schema's mention of list_sender_addresses.

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