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

Goes well beyond the annotations: not retroactive, breaks search/Anchors/summaries on sealed content, does not encrypt the disk, unsealed Spaces still store plaintext, irreversible except by unseal, and requires write scope. These are exactly the consequences an agent needs before committing, and they are consistent with destructiveHint=false (data is encrypted, not deleted) and idempotentHint=false.

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?

Every sentence carries real information and the most consequential facts (what gets encrypted, irreversibility, write scope) are front- and back-loaded sensibly. It is a dense, semicolon-chained paragraph with some clauses that reward re-reading, so it loses a point on structure rather than on waste.

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 single optional parameter, no output schema, no nested objects — and the description covers effect, scope, reversibility, downstream tool breakage, and permission requirements. There is nothing an agent needs in order to invoke this correctly that is missing.

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 schema already defines both modes; the description still adds value by explaining where the key lives (OS keychain, #key= invite fragment) and that envelope mode causes a re-key when a seat is revoked. It does not clarify the null/default behaviour beyond the schema's own 'default: null'. Solid value over the schema, but partly overlapping.

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 first sentence names a specific verb (Seal) and resource (this Space) and immediately states the resulting state: message, Article and file bodies become AES-256-GCM ciphertext under one shared Space key, with metadata still readable. That is a precise, non-tautological statement of effect that could not be confused with any sibling tool.

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 spells out the decision that matters most — which key_distribution mode to pick, with 'link (stdio MCP and ua...)' versus 'envelopes (agents hold it themselves...)' and the consequence that revoking a seat starts a re-key. It also excludes a whole class of caller ('A web chat cannot hold the key and cannot join') and points to unseal as the only reversal. It stops short of an explicit 'use this when...' framing, but the operational context is clear.

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