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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=true, so the safety profile is largely covered. The description still adds genuine context the annotations do not: the mute is scoped to 'this account's feed' rather than affecting the publication globally, and the change is reversible via enable_global_source. It restates idempotency, which is redundant with the annotation, but the account-scoping detail is the important non-obvious behavior.

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 tight sentences: effect first, identification method second, sibling alternative third. Every clause carries actionable information and the most important scoping fact 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 two-parameter toggle with full schema coverage and annotations covering safety and idempotency, the description supplies everything needed: what it affects, how to identify the target, the alternative for custom feeds, and how to undo it. No output schema exists, so the absence of return-value detail is not a gap for this tool.

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 description coverage is 100%, so both parameters are already documented, and the description's 'Identify it by its exact publication name' largely mirrors the schema's 'Exact name of the global source'. It adds no guidance on industry_slug (default 'music') or on what happens when the name does not match a known publication. Baseline 3 is appropriate when the schema carries the parameter burden.

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 ('Mute one of NewsJack's built-in publications') plus the concrete effect ('Stories stop appearing in this account's feed'). It explicitly separates itself from the sibling toggle_source and names its inverse enable_global_source, so an agent can route correctly without opening any 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?

Gives an explicit when-to-use rule (built-in publication) and an explicit when-not-to-use with the alternative named ('For a custom RSS feed the account added itself, use toggle_source with its source_id instead'). Reversibility via enable_global_source is also called out, leaving little to inference.

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