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

Adds behavior beyond the annotations: application is deferred ('Applied when the post is published'), a hard constraint (max 3 collaborators), and the LinkedIn caption coupling. Annotations only tell the agent this is a non-read-only, non-idempotent, non-destructive write. The description does not clarify replace-vs-append semantics on repeat calls, which matters given idempotentHint=false.

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 tightly packed sentences, front-loaded with the core action, then platform-specific rules, then the publish-time timing. No filler; every clause carries information an agent needs.

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?

No output schema exists, and the description covers both platforms, their constraints, and the timing of effect, which is sufficient to call it correctly. Minor gaps remain: whether mentions replace or append existing ones, and how to clear mentions once set.

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, but the description adds meaning the schema lacks: the max-3 limit on collaborators, that Instagram usernames are photo tags, and the cross-field rule that each LinkedIn mention requires '@<name>' in the caption. That cross-field constraint is real semantic value not expressible in the schema.

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 ('Add mentions/tags to a post') and breaks the behavior down per platform (Instagram photo tags/collaborators, LinkedIn { name, url } mentions). This clearly separates it from siblings like set_first_comment, edit_caption, and set_paid_partnership without the agent needing to open 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?

Gives clear platform-conditioned usage ('Instagram: ...', 'LinkedIn: mentions as { name, url } pairs') plus a prerequisite ('the caption must contain @<name>'). It stops short of naming alternatives or stating when NOT to use the tool, so it is strong context but not a full routing rule.

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