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

Annotations already declare a mutating, destructive, non-read-only, open-world operation, so the safety bar is partly covered. The description adds genuinely useful behavior — the operation is dual-mode and repeated tagging deduplicates to a single tag — but says nothing about permissions, failure modes for invalid IDs, or the fact that the remove path is the destructive one.

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?

Roughly 40 words, front-loaded with the purpose and followed by behavior notes. The first sentence ('Add a tag to a post, or take it off') and the second ('puts one of your post tags on ... or removes it') restate the same add/remove idea, so one sentence is slightly 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 a three-parameter idempotent-ish toggle tool with annotations covering the safety profile and no output schema, the description covers purpose, both modes, and multiplicity behavior. Only edge-case behavior (invalid tag, already-removed tag) is left unspecified, which is minor.

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 post_id, tag_id and remove are all documented in the schema itself. The description only reinforces the meaning of 'remove'; it adds no syntax, format, or sourcing detail beyond what the schema already states, so baseline 3 applies.

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 concrete verb+resource pair ('Add a tag to a post, or take it off') and scopes it to post tags on draft or published posts, which cleanly separates it from create_post_tag and tag_subscribers. An agent can identify the operation 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?

It gives context (works on draft or published posts) and explains that removal is done via the 'remove' flag, so usage is implied. However, it never names an alternative or a when-not condition (e.g. use create_post_tag to create a tag that doesn't exist yet) — that routing information only appears buried in the schema descriptions.

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