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

With no annotations, the description carries the transparency burden. It discloses that reads are counted, that the unguessable token is the credential, and that this is a read/serving operation separate from computing. It does not detail error behavior, but the output schema covers return shape.

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?

Purpose is front-loaded in the opening sentence, and the following paragraphs add necessary security and serving context. At roughly 90 words it is appropriately sized and every sentence contributes; slight verbosity in the MCP/JSON-RPC/npub enumeration keeps it from 5.

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 one-parameter read tool with an output schema, the description explains what it reads, why it exists, how the token authenticates, and that reads are metered. The only minor gap is no explicit mention of when to prefer sibling calendar tools, but the serving context covers that.

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?

The schema already documents 'token' at 100% coverage, so the baseline is 3. The description adds meaningful semantics by explaining the token is an unguessable credential because iCalendar subscriptions cannot carry a proof, which goes beyond the schema's one-line description.

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 specific verb ('Read') and resource ('stored calendar dataset') keyed by feed token. This clearly differentiates it from sibling management tools like calendar_list or calendar_revoke by focusing on retrieval for serving.

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 second paragraph gives clear context: this tool exists for the Good Earth site to serve a subscribable URL to calendar clients that cannot speak MCP or handle npub proofs. It does not explicitly name sibling alternatives, but the serving scenario is unambiguous.

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