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

Annotations already declare readOnlyHint=true, but the description adds significant behavioral context beyond that: the parishioner opt-in requirement, not-found response, and transcript withholding for unpaid sermons with price return. These are critical behavioral traits that annotations cannot convey. No contradiction exists between description and annotations.

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 three sentences, front-loaded with the main action and purpose. Each sentence carries essential information: primary function, availability constraints, and pricing behavior. No filler or redundancy. It is concise yet complete, achieving high information density.

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 two-parameter fetch tool with no output schema, the description covers all critical context: identifying the sermon, opt-in limitations, paid vs. free access, and the recommended purchase flow. It explains return variations (not-found, withheld transcript with price) without needing to enumerate metadata fields. Given the tool's simplicity and the supporting annotations, this description is fully adequate.

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 the baseline is 3. The description adds meaningful context for sermon_id by stating it's 'typically a sermon_id returned by search_sermons', which connects the tool to its sibling workflow. It also clarifies the include_transcript behavior by explaining when the transcript is returned (free or purchased) versus withheld. This goes slightly beyond the schema descriptions.

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 a specific verb ('Fetch') and resource ('metadata and optionally the transcript for ONE sermon by its id'). It explicitly distinguishes from siblings like search_sermons (which lists/search) and purchase_sermon (which buys). The scope ('ONE sermon') and the reference to 'sermon_id returned by search_sermons' anchor its unique role.

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 provides explicit usage context: use after search_sermons to get details for a specific sermon. It also gives an alternative/next step: 'call purchase_sermon first' for paid sermons. It explains when results are not available (opt-out pastors) and distinguishes free vs paid behavior, giving clear when-to-use and when-not-to-use guidance.

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