subscribe_digest

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

Discloses the double opt-in process (confirm link, confirmation required, one-click unsubscribe), consent safety, that no marketing flag is set, and the return format {ok, sent, message}. Annotations are minimal (readOnlyHint false), so the description carries the full burden and does so thoroughly.

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, then details. Slightly verbose but every sentence adds necessary context (consent flow, params, return, alternative). Could tighten redundant phrases like 'ONE call' and 'only call once' but overall efficient.

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 subscription tool with no output schema, the description explains the full flow, consent, param details, return values, and when to use. Covers all necessary context for an agent to invoke it correctly.

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 baseline is 3. The description adds minimal value: 'email (required)' restates the schema, and 'source (optional tag... e.g. mcp_digest)' adds a slight example but does not significantly enhance understanding beyond the schema.

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 clearly states the tool subscribes a human to a specific weekly digest (DC Hub's FREE weekly 'what changed' digest), with a specific verb ('Subscribe') and resource ('digest'). It distinguishes from siblings like 'set_market_alert' by detailing the digest content and consent flow.

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 provides usage context: 'Only call once your human shares their email and wants a weekly email.' It also advises preferring this over hand-building the POST request, giving clear when-to-use guidance and an alternative.

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