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

Annotations flag destructiveHint=true, and the description earns that: it discloses that link columns REPLACE visible linked records while records you cannot open stay, that an empty value clears rather than stores empty, and that an invalid value refuses the WHOLE call instead of partially writing. This is exactly the destructive/atomicity context annotations cannot express.

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?

Four front-loaded sentences, each carrying distinct information: format syntax, value-kind rules, replacement semantics, atomic failure. Dense with parenthetical examples but no filler sentences.

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?

A destructive mutation with no output schema, and the description covers input format, destructive scope, clear-vs-empty distinction, and failure behavior. Remaining gaps are permissions requirements and what a successful response contains, which are minor given the annotation coverage.

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 real meaning beyond the schema for `values`: country names or two-letter codes, link syntax (issue keys, wiki pages, page:471, thm:main, claim:12), comma separation, and empty-value semantics. Only field-name discovery (list_project_fields) is left unaddressed.

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 ('Fill in a project's own columns on one issue'), which distinguishes custom-field writes from generic issue updates. It does not name the closest sibling (update_issue) so the boundary must be inferred from 'project's own columns'.

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 opening clause makes the intended context clear: setting a project-specific custom field on a single issue, with example syntax supplied. There is no explicit 'do not use this for standard fields, use update_issue instead' exclusion, so the agent must infer the routing.

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