send_message

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

No annotations are provided, so the description carries the full burden, and it discharges it well on the consequential axis: content stays sealed during the tournament unless a participant leaks it, the realm always sees who corresponds / how many / how recently, and every private channel is unsealed at the closing ceremony. It omits auth/permission requirements and rate limits, keeping it short of a 5.

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?

Front-loaded with the core action and the mode-selection decision ('...in one call, OR give channel_id...') before the flavor text. The thematic phrasing ('sealed letters', 'closing gong') is verbose but still carries privacy-state information rather than empty filler, and the isolated 'Free.' is the only genuinely wasted token.

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?

With no annotations and no output schema, the description must cover mode selection, threading, and privacy consequences, which it does. It does not describe the response (e.g., returned message/channel IDs) or failure modes, but the schema already covers auth and content limits, so the remaining gap is minor.

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 the baseline is 3, but the description adds real meaning the schema lacks: to_kingdom_ids is one target for 1:1 vs several for a multi-party channel, channel_id is the mutually exclusive alternative, and reply_to threads onto a message in channel_id mode. The mode exclusivity is not expressed in the schema itself.

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?

States a specific verb+resource ('Send a private message') and then enumerates the two distinct send modes (to_kingdom_ids vs channel_id) plus threading. It also names the sibling that breaks the privacy contract (publish_channel), so an agent can distinguish this from read_channel/channels/publish_channel without opening schemas.

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?

Explicitly tells the caller which parameter to use for which situation: to_kingdom_ids for opening/reusing a 1:1 or multi-party channel, channel_id for posting into an existing channel such as an alliance channel. It stops short of naming when NOT to use this tool (e.g., routing public speech to post_statement/publish_channel as an alternative).

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