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

Annotations already convey read-only and non-destructive behavior. The description adds relevant context beyond those annotations: the links are time-limited, they expire, and renewal applies only to the interactive letter view. It does not describe the return format, but for a read-only helper this is a minor gap.

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 compact and front-loaded: scope, action, then trigger condition. The English translation is a deliberate duplication that improves accessibility without adding unnecessary fluff.

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 one-parameter, read-only, non-destructive helper, the description covers the main facts: what it does, when to use it, and its scope. It does not specify the exact return shape of the renewed URLs, but the tool name and verb make the outcome reasonably clear.

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 has one required parameter, letterId, with no description and 0% schema description coverage. The description never explicitly explains that letterId identifies the letter whose page link URLs should be renewed; this must be inferred from the tool name and the word 'Briefseiten'.

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 states a specific action ('renews the time-limited image links'), a specific resource ('letter pages in the interactive letter view'), and an explicit scope boundary ('Nur fuer die interaktive Brief-Ansicht'). This distinguishes it from sibling page-URL tools for approvals and templates.

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?

It provides an explicit trigger condition ('when the old ones have expired') and an explicit when-not constraint ('only for the interactive letter view'). An agent can confidently decide when to call this tool and when to look at other view-specific tools.

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