post_message

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

Annotations already declare readOnlyHint=false and destructiveHint=true, so no contradiction. The description adds a non-obvious behavioral detail: when blocks is provided, message serves as the plaintext fallback, and blocks must be a JSON string. This goes beyond the structured fields and helps the agent predict rendering behavior.

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?

The description is two focused sentences with no filler. The core operation is front-loaded, and the Block Kit fallback detail is delivered in a compact, scannable way. Every sentence adds value.

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 tool with 7 parameters and 0% schema coverage, the description is adequate for the simple send-message case but incomplete for advanced usage. It explains blocks well but omits meaningful behavior for thread replies and link unfurling. The presence of an output schema reduces the need to describe return values, but the missing optional parameter semantics remain a gap.

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 0%, so the description carries the burden of explaining parameters. It explains blocks and its relationship to message, but does not clarify thread_ts, skip_log, unfurl_links, or unfurl_media. Those parameter names may be suggestive, but an agent cannot reliably determine their semantics from the description alone.

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 uses a specific verb and resource: 'Post a message to a channel.' It clearly distinguishes this from sibling DM tools like send_dm and send_group_dm, and from post_command by framing the operation as a message. The Block Kit mention adds meaningful scope without ambiguity.

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 makes the target context explicit ('to a channel'), so an agent can infer this is the right tool for channel messages rather than direct messages. It does not explicitly name alternatives or state when not to use it, but the channel scoping is sufficient for basic routing.

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