agent_join_channel

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

With no annotations, the description carries the full burden and does so richly: it discloses the side effect (members can see who joined), the gating requirement (env var), the encryption model (relay-held key, relay can read posts), and identity semantics (acts as the identity in the local credential store). This is substantial behavioral context an agent cannot get from structured fields.

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?

Five short sentences, front-loaded with purpose, then side effect, gating, and privacy/identity notes. Each sentence is relevant, though the delivery is terse and slightly choppy.

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 mutation tool with no annotations and no output schema, the description covers the critical gating, side effects, and privacy implications. Minor gaps remain (error behavior, whether an invite is required), but nothing essential for correct invocation 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% and the sole parameter (channel_id) is already documented in the schema as "Channel id." The description adds no format, syntax, or sourcing guidance beyond that, so the baseline of 3 applies.

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 opening sentence states a specific verb and resource ("Join a channel"), which is distinct from siblings like agent_create_channel, agent_list_channels, and agent_post_to_channel. It does not explicitly name an alternative (e.g. agent_respond_invite for accepting an invite), but the core action is unambiguous.

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 description gives a concrete precondition: it is off by default and refused unless the human owner set VOIDLY_MCP_RELAY_ALLOW_STATE_CHANGES=1, which is real when-it-will-fail guidance. It does not, however, route the agent among alternatives such as accepting an invite via agent_respond_invite.

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