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

Annotations already declare the mutation and safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=true). The description adds real value on top: the key naming convention (platform or platform:account_id) and the assurance that other post fields survive the call, which is the key behavioral fact for a partial update.

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, no filler, and the core operation is front-loaded ahead of the key-format and preservation details. Every sentence carries information the 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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. The description supplies the key format and non-destructive partial-update semantics; it could still say whether validation or a publish step follows, but it is otherwise complete enough to invoke correctly.

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 only 50% (post_id is undocumented), so the description has to compensate, and it does so for the non-obvious parameter by spelling out exactly what the object keys must be: 'platform names or platform:account_id'. Only post_id is left implicit, which is a minor gap given its self-evident name.

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 pairs a specific verb ('Tailor captions') with a clear resource scope ('per selected platform or account'), and the closing clause 'Other post fields are preserved' implicitly separates it from update_post. It does not explicitly name the sibling, but an agent can still tell this is a per-platform caption override rather than a general post edit.

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?

Usage is implied: reach for this when captions must differ per platform instead of a single shared caption. There is no explicit 'use X instead when...' guidance and no mention of prerequisites such as the post being a draft or needing validation against platform rules, despite validate_post and get_platform_requirements existing as siblings.

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