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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds two pieces of context the annotations do not: the required scope `calendar:read`, and a prompt-injection warning that user-authored text arrives in untrusted_fields and must be displayed, never obeyed - a meaningful behavioral disclosure for a tool returning user-supplied strings.

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?

Two short sentences: purpose first, then auth plus the trust-boundary note. Nothing is padded, and the most actionable information (what it returns, what permission it needs, how to treat returned text) is front-loaded.

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 zero-parameter, read-only getter with no output schema, the definition covers purpose, required scope, and handling of untrusted content. The minor gap is that it does not say what form the link takes or how it relates to rotate_calendar_feed, which would matter if the link is ever exposed or regenerated.

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 tool accepts zero parameters, so there is no parameter semantics to explain and the baseline is 4. The description correctly spends no text on nonexistent inputs.

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?

States a specific verb and resource ("Get my calendar subscription link") that an agent can match against siblings such as create_calendar_feed, rotate_calendar_feed, and export_calendar. It does not explicitly name those alternatives, so the differentiation is implicit rather than spelled out.

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 name and description imply the use case (the caller wants the personal calendar subscription URL), but there is no explicit when-to-use vs. when-not framing. In particular, nothing distinguishes retrieving the feed from rotating it (invalidating the old link) or creating one, which is the most likely confusion among the sibling tools.

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