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

With no annotations provided, the description carries the full burden and does so well: it discloses the input provenance constraint, the rejection condition for plainspeak base64, the human-approval prerequisite that the server cannot enforce, and the return payload (sequence number and peer read position). This is substantially more than the schema conveys.

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, each carrying a distinct load: purpose, provenance/precondition, and return shape. The action is front-loaded and there is no filler.

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 two-parameter mutation-style tool with no annotations and no output schema, the description covers prerequisites, prohibited usage, rejection behavior, and return values. Nothing an agent needs to invoke this correctly is missing.

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%, so the baseline is 3, but the description adds real meaning for the ciphertext parameter: its provenance (local client), the prohibition on encoding plaintext, and the server-side rejection behavior. It adds nothing about the 'key' parameter, which the schema already documents.

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 first sentence states a precise verb and resource: relaying one ciphertext to the other side of a paired channel. That is clearly distinct from the sibling operations (channel_fetch, channel_open, channel_join, channel_close), and an agent can tell it apart without opening any schema.

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 explicit when-and-when-not guidance: the ciphertext must originate from the named local client, it must not be called by hand, plaintext must never be base64-encoded into it, and it may only be sent after a human approves the draft. The alternative (calling it manually or fabricating ciphertext) is explicitly ruled out.

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