Set what's new

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

Annotations already declare idempotentHint=true and destructiveHint=false, and the description adds real context beyond them: it names the external system mutated (App Store Connect), the required write credential (ASC_WRITE=1), and clarifies that re-runs skip completed steps. Return/result behavior is not described, keeping it out of 5 territory.

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?

Three short sentences, front-loaded with the purpose and target semantics, followed by the mutation target and safety note. Nothing redundant.

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 an 8-parameter write tool with no output schema and 75% schema coverage, the description covers purpose, both target modes, auth requirements, and idempotency. It omits only what a successful result contains and how the text length limit interacts with target selection.

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 75%, and the description supplies the one genuinely undocumented enum meaning: what 'app_store' vs 'testflight' do to text. That adds value beyond the schema, though the interplay of locale/platform/version with each target is left implicit.

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 ('Sets release notes') and immediately disambiguates the two modes: app_store writes the version's What's New, testflight writes a build's What to Test. No sibling tool covers release notes, so the agent can identify the capability without opening the schema.

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 target semantics effectively tell the agent which mode to pick for a version vs a build, and it flags the ASC_WRITE=1 prerequisite. It stops short of naming alternatives or stating when not to use it (e.g. versus update_listing), but the context is clear.

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