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

Despite the destructiveHint annotation already flagging mutation, the description adds substantial behavioral detail: 'Never leaves two live URLs,' 'Refuses a new slug ending in a year,' and 'renaming republishes' when drafts are ahead. These go well beyond the annotation and fully disclose side effects and constraints.

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?

Two sentences, zero filler. The action is front-loaded, followed by invariants and refusal conditions, then the usage alternative. Every clause earns its place.

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 simple three-parameter mutation with no output schema, the description covers purpose, side effects, refusal conditions, and the alternative. The only minor gap is not stating what the tool returns on success, but this is not critical given the simplicity and the behavioral richness already provided.

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%, with each parameter having a meaningful description ('The article shelf. Slug changes do not move shelves.', 'The new slug. Must not end in a year.'). The description reiterates the year restriction but adds no new parameter-level information, so the baseline of 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?

The description clearly states a specific action ('Change an article slug') with a concrete resource (the article), and explicitly names the primary side effect (301 redirect). It also distinguishes itself from the alternative of saving a second article under a new slug, making its purpose unambiguous against sibling tools.

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 description explicitly says 'Use this instead of saving a second article under a new slug,' giving a direct alternative. It also enumerates three refusal conditions (year-ending slug, slug already in use, draft ahead of published), which serve as clear guidance on when not to use the tool.

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