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

Annotations already declare destructiveHint=true and idempotentHint=true; the description earns credit by explaining the real damage model: omitted fields are preserved, and "Sending slides replaces the whole list" warns that the one list-valued field is wholesale replacement rather than a merge. It adds scope and replacement semantics without contradicting the destructive hint.

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?

Front-loaded with the verb and full field list, then three short constraint sentences. Slightly dense enumeration in sentence one, but every subsequent sentence adds a non-obvious rule rather than restating the schema.

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 15-parameter mutation with no output schema, the description covers the essentials an agent needs: partial-update preservation, list replacement semantics, the primary-post rule, and the redirection of local file uploads. It says nothing about what the call returns or about permission/validation failures beyond the project-name ambiguity already noted in the schema.

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 baseline is 3, but the description goes beyond it in two places: it prescribes that per-slide text belongs in slides and "never in the publishing notes," and it defines what is_primary means in workflow terms (the one post that advances its script). Those are routing decisions the enum and types alone do not convey.

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 opening sentence names the verb and resource precisely ("Change a post on the content calendar") and enumerates the mutable surface: timing, type, title, platforms, primary flag, status, captions, slides, media links. It is clearly the mutation counterpart to create-content-schedule, though it never names a sibling explicitly.

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 partial-update contract is stated plainly ("Anything you leave out stays as it is"), and media-from-disk work is explicitly routed away to the prepare/confirm upload flow instead of being attempted here. It lacks an explicit when-not statement such as preferring get-content-schedule to read current values first.

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